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for the Chemical Analysis of the Principal Industrial and Food Products



Director of the Chemical Laboratories of the Italian Customs



















University of Birmingham

VOL. 11.











••. ;



, *


In the preparation of the present translation, the points on which it has been considered desirable to depart from the sense of the Italian text are few and mostly unimportant. Notification is made where any appre- ciable addition to or modification of the original has been made to bring it into conformity with the conditions in this comitry.

Temperatures are always expressed in degrees Centigrade, and concen- trations of aqueous alcohol solutions, according to the French custom, in

percentages by volume.

THOMAS H. POPE. Birmingham.

4.5€»i 6




Chap. I. ^Meat and its Preparations ....... i

Meat ............ I

Sausages 3

Meat extracts .......... 10

Tinned meats .......... 17

Chap. II. ^Mllk and its Products 22

Milk ............ 22

Table I. Standards for milk in Italian cities .■ . -30

Preserved milk .......... 32

Butter 35

Table II. Distinctive reactions for butter colouring matters . 40

Table III. Mean composition of butters .... 43

Skim milk butter ......... 43

Artificial butter .......... 44

Cheese ........... 44

Chap. III. Flour, Starch, and Derived Products .... 49

Flour ........... 49

Table IV. Compositions of wheat offals .... 68

Bread 68

Macaroni, vermicelli, etc. ........ 73

Table V. Examination of yellow dye in macaroni, etc. 76

Starches ........... 77

Dextrin ........... 79

Chap. IV. Sugars and Products containing them .... 82

General methods .......... 82

Hydrometric method . . . .82

Table VI. Relation between degrees Brix and the specific

gravity at 17*5® C. ....... 85

Table VII. Relation between degrees Brix and the specific

gravity at 20® C. . . . . . . . .88

Table VIII. Correction of degrees Brix to 175** C. . 91

Table IX. Correction of degrees Brix to 20° C. . .92

Refractometric method ........ 93

Table X. Relation between refractive index and concentration

of sugar solutions ........ 94

Table XI. Temperature correction of the refractive index 95

Polarimetric method ........ 9^

Chemical method ......... 108



\ V V


^.^ .,*n{*j>yii*img with copper reduced (Allihn) "^.^ -^-Ai aici«HP*»*^^ ^^^ copper reduced

^ sc^ .v.i*ft4»«Hiing with copper reduced (Wein)

, .>v .>^ »4^s4Wttdiag with copper reduced (Soxhlet)

...>,*-. ^ o* thi? principal sugars

^ >*^ija>^ lu their mixtures


v'l the sugar industry

1* "^ *>

* »

h4NV4* AU^w oonrcspondingwith b^vlvMai Ko* the calculation of

\ V

,x, ^ v*xt x^unUvs( nmtH


uvU>\*¥^^ow« mibitances v.vvv^wvs^\Mi UIW miUitwioes

copper (Herzfeld) invert sugar







[22 22

23 26

L29 129

31 32 33 36 36

:39 40




41 43 45 45 45 49 [49

52 56 56

57 58

58 59

[64 :64



[66 :67 [67 [68 [68 [68 [69 [69 [69


71 72




Forcing test Determination of arsenic

Chap. VI. ^Wlne






Elxtemal examination Specific gravity Alcohol content .

Table XXI. Alcohol table Extract .... Table XXII. Extract table Determination of ash

alkalinity of the acidity tartaric acid sugars Detection of dextrin and impure glucose Determination of the glycerine Measurement of the colour Detection of extraneous colouring Determination of the sulphates M ,, chlorides

Investigation of the nitrates . Determination of the phosphoric acid Detection of citric acid

,, free mineral acids

Table XXIII. Values of a : 6 Detection and determination of antiseptics Detection of artificial sweetening agents

and determination of extraneous metals Microscopic examination .... Vinegar .....


Chap. VII. Spirits and Liqueurs


General methods .......

Objective characters .....

Determination of alcohol ....

Table XXIV. Alcohohc strength from specific gravity Determination of the extract and ash . Detection and determination of impurities

Table XXV. Dilution of alcohol to 90% strength Table XXVI. Strengthening of dilute spirit to 50%

centration by means of 90% alcohol Table XXVII. Dilution of strong alcohol to 50% concentra tion .......

Determination of the acidity.

,, esters ....

Detection and determination of the aldehydes

furfural . Determination of the higher alcohols Detection and determination of metals .

denaturahts . methyl alcohol Special pari ........

Industrial spirit .......

Table XXVIII. Composition of industrial spirits

f (



PAGE 172

176 177


182 184 189 190 191

194 196

197 199















230 230 230

234 238

238 238





244 246




258 260




. >


.^ \\l\ »,uiup^tions of eaux-de-vie

. ..V \\\ V inupositions of cognacs

, .^^ \\\l icoiupoaitions of genuine rums

/., \\\U Cuiupoaitions of fruit spirits

> u. \\\m CumiK)sitions of whisky and gin

VHi^^u«a uu

iSuuuuiui^v^i K»t U\«^ specific gravity .

rotatory power rt^fractive index iH>lidifying point . lK)iUng point Kolubility

(iHtera .... fifo alcohols aldehydes . phenols

t «<

«< ««

41 II


\ II V^

( l\ivnult*rH and compositions of the

\ \^v^

PtiuiUlri* and Iwiling points of nuurttltMH ot Holvents for varnishes

\ ^^W

' * *

\ v»mu* ' '


solvents for



263 263 265


266 266

269 269 270 270


274 275

275 275



278 278

279 280












299 301 306 309


313 314

317 317

321 321

324 325 329 329



Chap. XII.— Tanninft ProducU

Prime materials and tanning extracts Qualitative examination

Table XXXVII. Reactions of tanning substances Quantitative analysis

Table XXXVIII. Compositions of tanning materials

Tannin ....•••••



331 331 334 337 346 346

Chap. XIII.— Inks

Qualitative tests . Quantitative analysis Practical tests


348 352- 353

Chap. XIV.— Leather

Tanned leather ......•■

Physical and mechanical tests . . . . .

Chemical analysis .......

Table XXXIX. Compositions of various sole leathers Chromed leather ........

Physical and mechanical tests . . . . .

Chemical analysis .......




357 362

364 364 364

Chap. XV. Colouring Matters

Mineral colours (pigments)

General methods .....'••

Technical tests .......

Chemical analysis ......

Special part ......•••

White pigments .......

Table XL. Scheme for the recognition of white pigments White lead ........

Zinc white ........

Lithopone ........

Permanent white .......

Red and yellow pigments ......

Table XLI. Scheme for the recognition of red and yellow pigments .......

Chrome yellow, Chrome red .....

English red ........

Ochres .........


Cinnabar, VermiUon ......

Cadmium yellow .......

Green and blue pigments ......

Table XLII. Scheme for the recognition of blue and pigments .......

Ultramarine ........

Prussian blue, Tumbull's blue .....

Greens and blues with a copper basis

Chrome green ........

Mixed chrome greens ......

Terre verte ........



366 366 366

370 372 372 373 372 375 377 378 379


379 381

383 384 386

387 388

389 390 392 393 395 395 396



Brown, grey and black pigments ...... 396

TaUe XLIII. Scheme for the recognition of brown, grey and

Uack pigments ........ 397

Umber ........... 398

Cologne earth .......... 399

Graphite ........... 399

Black pig^ments with a basis of carbon ..... 400

Metallic pig^ments ......... 40Z

Lakes. ........... 402

Organic colouring matters 404

Dye woods and barks and their extracts .... 405

Logwood extract 407

Red wood extract 409

Yellow wood extract 410

Quercitron extract 410

Indigo 41 z

Indigo carmine ......... 416

Alizarin ........... 416

Catechu, Gambier 419

Cochineal 420

Carmine 421

Artificial organic colouring matters .422

Identification of colouring matters. ..... 424

Table XLIV. Basic and basic mordant dyestufifs - 4^7

Table XLV. Salt and sulphur dyestuffs .... 428

Table XLVI. Acid and acid mordant dyestuffs . . 430

Table XLVI I. D3restuffs insoluble in water . 432

Table XLVIII. Reducible and non-reoxidisable dyestuffs . 434

Table XLIX. Reducible and reoxidisable dyestuffs . 435

Table L. Non-reducible aminic dyestuffs .... 436

Table LI. Non-reducible phenolic dyestuffs •437

Detection of extraneous substances in colouring matters. . 438

Tintorial value of colouring matters ..... 440

Chap. XVI. ^Textile Fibres, Yams, Fabrics 441

Microscopic examination . -441

Table LII. Microscopic characters of vegetable fibres. . 445

Table LIII. Microscopic characters of animal fibres . -451

Chemical examination . -435

Tables LIV. LV. LVI, LVII, LVIII. LIX, LX. Identification

of colouring matters on wool . '477


Identification of colouring matters on cotton . 497

Physico-mechanical examination ...... 528

InDKX to THe];TwO VoLUMW t t r $29



In its ordinary meaning, the term meat is applied to parts of slaughtered animals consisting principally of muscular tissue together with larger or smaller quantities of tendons, adipose tissue, bone, etc.

The examination of meat concerns in the first place the food inspector, whose duty it is to determine that the meat is good for food and has not been obtained from diseased animals. The analyst's task is usually to determine the nutritive value of the meat by estimating its principal com- ponents and to test for the presence of preservatives or colouring matters. The more common chemical tests and determinations are as follows :

Sampling. About 500 grams are required, and this quantity is usually taken from several (3-5) of the more fleshy parts of the carcase. The pieces are freed from bone, cut into pieces a few grams in weight by means of a knife and then converted in a mincing machine into a fine pasty mass, which is well mixed so as to give a homogeneous sample.

1 . External and Objective Characters. Observations are made of : the colour (whether bright red or brownish-red), the consistency (whether compact and elastic or the reverse), and the odour (whether normal and not unpleasant, or, on the other hand, indicative of putrefaction). Note is also made of the odour and taste of the broth obtained by boiling a piece of the meat with water in a closed vessel the odour at the moment the liquid begins to boil. Observation is also made of the reaction whether this is amphoteric, or acid, or alkaline ; the last indicates putrefaction.

2. Determination of the Water. About 10 grams of the prepared sample are weighed exactly in a flat porcelain dish, the fragments being spread over the whole surface of the dish, which is left in a steam-oven for about four hours and then transferred to an air-oven at 105**. After a further two hours the dish is cooled and weighed and then heated for about another hour, after which the weight is usually found to be unchanged.

The moisture in meat may also be calculated by subtracting from 100 the sum of the percentages of fat, albuminoids and ash.

3. Fat. This may be determined on the dry residue from 2, which is placed in a filter-paper thimble in an extraction apparatus, while the dish is rinsed out with anhydrous ether or light petroleum into the extraction flask. The extraction is continued for about six hours, after which the bulk of the solvent is distilled off on a water-bath, while the remaining

AX. 1 I


liquid is then evaporated at a gentle heat in a tared glass dish and the residual fat dried for two hours in a steam-oven, cooled and weighed.

4. Nitrogenous Substances. These are determined by Kjeldahl's method, as follows :

About 07-0 '9 gram of the dried and defatted or only dried meat is gradually heated to boiling in a Kjeldahl flask with 10 c.c. of concentrated sulphuric acid and about 0-5 gram of copper oxide, the boiling being con- tinued until the substance is completely attacked, this requiring about two hours. Finely powdered potassium permanganate is then added to the hot liquid imtil the latter assumes a greenish-brown tint. The cold liquid is diluted with water, placed in a distillation flask, treated with 40 c.c. of 50% caustic soda solution, and about 100 c.c. distilled over into 15 c.c. of semi- normal sulphuric acid {see Fertilisers, Vol. I, p. 122). The excess of acid is titrated with N/2 -alkali in presence of methyl orange : i c.c. N/2 -sulphuric acid = 0-00702 gram of nitrogen, and i gram of nitrogen = 6-25 grams of albuminous matters.

The latter calculation, based on the supposition that all nitrogenous sub- stances of animal origin contain 16% of nitrogen, is not quite exact, but it gives results which are usually satisfactory and are very near to the percentages of nitrogenous compounds calculated by difference : the sum of the moisture, fat and ash being deducted from 100.

5. Ash. In a fairly large platinum dish a weighed amount (about 10 grams) of the meat is carefully charred, the carbonaceous mass being twice triturated with a small, clean pestle. When charring is complete, the mass is treated several times in the dish with small quantities of hot water, which are then poured on to a small filter. The residue on the filter is washed well with a little water and the filter and its contents placed in the platinum dish, dried and completely incinerated. To the ash thus obtained is added the liquid from the lixiviation of the carbon, the whole being evaporated to dryness on the water-bath and the residue gently ignited, cooled and weighed.

The qualitative analysis of the ash is carried out as usual.

When a quantitative determination of the phosphoric acid and chlorine is required, a fresh quantity of ash is prepared from a weighed amount of the meat sample mixed with an alkali such as milk of lime, sodium carbonate, etc. The phosphoric acid and the chlorine are determined in the nitric acid solution of the ash, the former by the ammonium molybdate method, and the latter either volumetrically or gravimetrically as silver chloride.

6. Detection and Estimation of Preservatives. The antiseptics commonly tested for in meat are formaldehyde, formic acid, boric acid and fluorides. The analytical methods used for the detection of these and other antiseptics are given later [see Sausages).

7. Colouring Matters. 50 granr.s of the meat are well shaken in a beaker with a solution of sodium salicylate in aqueous glycerine (5 grams of the salicylate in 100 c.c. of a mixture of water and glycerol in equal volumes), the beaker being heated on a steam-bath for half an hour. The cold mass is filtered through linen and the solid matter pressed, the liquid **-^ng then filtered through paper until clear.


If the filtrate is yellowish and not reddish, the absence of colouring matter is at once concluded. With a reddish filtrate, about one-third of this is treated in a cylinder with a few drops of alum solution and then slight excess of ammonia : if after a rest of some hours the precipitate is red, the presence of carmine is indicated.

With the remainder of the liquid, mixed with lo c.c. of io% potassium bisulphate solution and a few drops of acetic acid, two or three strands of well-defatted wool are heated on a water-bath for a long time. In presence of coal-tar dyes, the wool is coloured red, the colour persisting after washing with water.

Meat, as defined above, varies widely in composition, not merely with the individual animal yielding it, but also according to the breed, age, etc., of the animal, to the part of the body from which it is obtained, and to the method of slaughtering employed. The total nitrogenous substances are mostly about 20%, and the fat and water vary together, the one increasing as the other dimin- ishes ; for instance, fat beef with 32-50% of water may contain 55-1% of fat, while lean meat with 74-20% of water may contain only 3-45% of fat.

The ash amounts to almost 2% and contains mainly potassium phosphate, with less proportions of calcium and magnesium phosphates and sodium chloride.

Freezing does not appreciably modify the composition of meat ; it causes the loss of a little water (not much more than 1 %) but no change in the nitro- genous substances and fat.


The objects of chemical analysis are the same with sausages as with fresh meat, and the various determinations are made in the same way. For detecting certain special adulterations the following methods are used :

1. External and Objective Characters. The appearance, odour and taste of the meat are compared with those of the corresponding fresh meat, note being taken of the retention or otherwise of the more or less deep red colour of the muscular parts ; the fat is observed to ascertain if it is white and of pleasant odour, and the mass of the meat to see if it is compact and without empty spaces and not excessively moist.

Any mould completely or partially covering the surface is noted. When such is present, the interior often contains somewhat soft masses of rancid, bitter taste and disagreeable odour which, when cut, reveal lean parts of a grey or greenish colour and fat coloured yellow or greenish. These indi- cations denote fairly advanced putrefaction ; often, however, the signs of putrefaction in its initial stages are apparent to a less degree or not at all, and in such cases the changes are detectable only by bacteriological examination.

2. Water. This is determined as in fresh meat (2, above).

Sausage meat is not infrequently rich in water, which is added fraudulently ; water is also added with starch paste and in such a case this determination is of special importance.

3. Determination of the Acidity of the Fat.*— From 5 to 8 grams of

* Schweiz: Wockenschrift f. Chem. u, Pharm,^ 1910, XLVIII, p, 481,


the finely minced mass are mixed with well washed sand and treated with ether, the ethereal solution of the fat being filtered and made up to 50 ex. ;

5 c.c. are evaporated in a tared glass dish and the residue dried for 45

minutes in a steam-oven and weighed. The remaining 45 c.c. are mixed

with 45 c.c. of 45% alcohol and the acidity then titrated with N/io-caustic

soda in presence of phenolphthalein. If a represents the weight of the

dried residue from 5 c.c, of the ethereal solution and b the number of c.c.

of alkali used in the titration, the degree of acidity of the fat expressed in

normal alkali is given by the formula,

. 10b A =

4. Detection of Albumin (Casein, Egg Albumin). Albumins may be added to render the meat paste more dense and compact. They may be detected as foUows :

(a) According to Feder,* the presence of casein is shown by a high pro- portion of Ume in the ash, defatted meat containing only o*o6-0'i3% of lime, whilst casein contains about 2%. 10 grams of the sample are care- fully defatted, the residue being incinerated and the ash dissolved in dilute hydrochloric acid ; the acid liquid is treated with ferric chloride and sodium acetate to eliminate the phosphoric acid, and then heated until all the pre- cipitate is thrown down, boiled and filtered. In the filtrate the lime is determined by means of ammonium oxalate in the usual way.

(6) Albumin may be detected by the marked alkalinity of the ash, since commercial albumins mostly contain alkali. Thus, while the alkalinity of 100 grams of dry pork is 81 c.c. of normal acid, the addition of 1% of commercial albumin increases it to 20 c.c.

5. Detection and Determination of Starch. {a) Qualitative iesL A freshly-cut surface of the sample is treated with a few drops of iodine solution to see if a blue coloration is formed. If the result of this test is doubtful, a quantity of the dry, defatted substance is triturated well with a little water, and after depositing for a short time, the turbid Uquid examined under the microscope. A little iodine solution is then added and the speci- men again examined microscopicaUy for stained starch granules.

(b) Quantitative determination? 10 or 20 grams of the sample, according to the intensity of the iodine reaction, are heated on the water- bath in a covered beaker with 50 c.c. of 8% alcoholic potash solution, the liquid being frequently stirred. As soon as the mass is dissolved, the liquid is diluted with 2-3 volumes of hot 50% alcohol and, after standing for some time, filtered through a Gooch crucible containing asbestos.

The contents of the crucible are washed twice with hot 8% alcoholic potash and then with 50% alcohol until the filtrate ceases to give an alkaline reaction and remains clear on addition of acetic acid ; the washed precipi- tate is heated for about half an hour in the original beaker on a water-bath with 60 c.c. of 6% aqueous potassium hydroxide, with frequent stirring. The cold hquid is made up to 200 c.c, allowed to settle thoroughly, and go c,c, of it acidified in a beaker with acetic acid and treated with an equal

^ 2fsitschr. Uni. Nahr- und Genuss-miUel, 1909, XVII, p. 191, f ^fay^hpf^r : fofschun^sber,, III, 1896, pp. 141, 4^9,


volume of 96% alcohol, which precipitates all the starch. The precipitate is collected in a tared Gooch crucible and washed thoroughly with 50% alcohol, then with absolute alcohol and finally with ether.

The crucible is dried first at 40° and then at 100° to constant weight, being subsequently calcined, cooled and again weighed ; the difference between the two weights gives the starch free from ash and water. To express this value as potato starch, etc. (which is what is usually added), it is divided by o-8 ; to express it as cereal flour, it is divided by 0-67.

This method precipitates also the small quantity of glycogen in the meat ; as a rule this does not influence the results appreciably, but when the separation of starch from glycogen is necessary, especially in presence of horseflesh, Mayr- hofer's modified method is used (see later).

It should also be noted that part of the starch found may be derived from the spices used, this being allowed for by subtracting 0-5% of the quantity found.

6. Detection of Horseflesh. The methods here used are based on the detection and determination of the glycogen and on an examination of the fat.

A. Detection and Determination of the Glycogen :

1. Qualitative test. Two cases present themselves :

(a) Absence of starch : about 50 grams of the sample are subjected to prolonged boiling with 200 c.c. of water. When cold, the liquid is decanted off, treated with dilute nitric acid to precipitate the albuminoids and filtered. A little of the filtrate is treated in a test-tube with a few drops of a very dilute solution of iodine in potassium iodide ; in presence of glycogen the liquid assumes a bright red colour, which disappears at 80-90*" and reappears on cooling.

Feeble or transitory colorations should be disregarded, since other flesh than that of the horse may contain small proportions of glycogen. The colora- tion should be sharp and decided and such is obtained with fresh horseflesh or with sausage containing it, if recently prepared ; the glycogen gradually disappears with lapse of time and the reaction becomes continually less marked.

Further, this coloration is not characteristic of glycogen, but is shown also by certain dextrins, which behave hke glycogen on heating.

{b) In presence of starch, glycogen is tested for as follows : A portion of the sample is heated on the water-bath with 8% alcoholic potash until the fleshy mass is dissolved. The liquid is filtered off with the help of a pump and the residue on the filter washed with cold 95% alcohol and then boiled with 96% alcohol, which partially dissolves the glycogen but leaves the starch undissolved. The filtered liquid is evaporated on a water-bath, the residue taken up in a little water and the solution tested for glycogen by means of iodine.

The detection of glycogen in presence of starch is not easy, and even the above method often gives uncertain results. In such cases use is made of biological tests for horseflesh.

2. Quantitative estimation. The following procedure is employed^:

* Mayrhofer and Polenske : Zeitschr, Unt. Nahr-und Genuss-mittel, 1901, IV, p. >7, XIII, 355.




|.j^^ . - ..KTent fat, are heated in

gll .-- >.a:. of alcoholic potash (80

,\. 'o ^cohol), the liquid behig - .issolved.

>;.• '^, alcohol, the impure glycogen .^.jutate is washed with 30 ex. of ,.. 10% alcohol until the filtrate is . A itrw drops of dilute hydrochloric with 50 c.c. of normal potash on ive the glycogen. When cold the vaic acid, made up to no c.c. with

Av; 150 ex. of absolute alcohol and after . .,ui IS collected on a tared filter, washed

V .. abs«.)lute alcohol and ether, dried at . wv i^ht. The weight found, multiplied

.. V vi white, amorphous powder and its ,. K.vvl white opalescence, should not reduce ^.\o sUi intense burgundy-red coloration

'.N ,»alv in absence of starch.

X . Horse fat differs from the fats of other

. > si Mid iodine number.

. . XV.) i^iams of the sample the fat is separated

, . . S\ b<>iling with water and separating the

V ...usvl in the Zeiss butyro-refractometer at

i \lw iudox exceeds 51-5**, the presence of

, ^ .u uumlH^r (see Fatty Substances, Vol. I) vvvvt=^ >*» ^***' presence of horseflesh may be

IV .U ^\ \ honucal methods based on detection

yM vUo M*iructive index and iodine number

V. .^^iv* . the presence of glycogen and the

, lUvl^v^Ouu^s, but definite proof is possible

\\ \ .^^N^^^u^i nu'Jits, the detection of horseflesh

. v\aU U%''*\\ nvt^at, since they mostly consist

^^ .uu<^K^ \^ Preservatives.

v^ Iho finely minced sample are


\ { Mws's^W"^ Hand and a few c.c, of water

4. uxvi\ hron>* paste. The whole is poured

\. .\ \\^<* « •*•* " l^*'^^* ininuti^ to coagulate

0^0 l^^jui^l brnuurs ulmast colourless.

»M, wV^\N< ^^ nllrird and the chlorine esti-


mated by Volhard's method (see Vol. I, p. lo, Potable Water) on 25 ex. of the filtrate.

(6) Potassium Nitrate. For the qualitative test, about 20 grams of the dried fleshy mass are freed from fat by treatment with ether or petro- leum ether, the residue being shaken vigorously with 20-30 c.c. of very hot water and filtered. A certain amount of the filtrate is added gradually to a ciystal or two of brucine and a little pure concentrated sulphuric acid in a porcelain dish : a distinct red coloration indicates nitrates.

For the quantitative determination, this method is carried out as follows : Reagents, [a) 025 gram of crystallised brucine is dissolved in cone, sulphuric acid free from nitric acid, the solution being prepared in a 100 c.c. cylinder and made up to the mark with the sulphuric acid. This solu- tion should be recently prepared.

(b) o-io gram of pure potassium nitrate is dissolved in a little water and made up to a litre.

(c) 5 grams of mercuric chloride are dissolved in 100 c.c. of distilled water and 100 c.c. of 2% hydrochloric acid added to the solution.

Standard solutions. Of solution (6), 5, 6, 7, 8, 9 and 10 c.c. are intro- duced into porcelain dishes together with 5, 4, 3, 2, i and 0 c.c. of water respectively and then, at once. 20 c.c. of solution {a). After being mixed for a few moments, each liquid is poured into a glass cylinder with a ground stopper, in which it is shaken with 70 c.c. of distilled water. This series of coloured solutions should be prepared as nearly as possible at the moment it is required.

Procedure. 50 grams of the sample are weighed out and boiled for 30 minutes with 200 c.c. of water. When cool, the liquid is filtered by decantation into a 500 c.c. flask and the residue treated again with two or three quantities of 100 c.c. of water, the volume being subsequently made up with distilled water in the flask.

To 50 c.c. of the turbid liquid are added 50 c.c. of solution (c), the mixture being filtered. 10 c.c. of the liquid thus obtained are poured into a dish and immediately treated with 20 c.c. of solution (a), the liquid being mixed, poured into a cylinder of similar dimensions to those used for the standard solutions and mixed with 70 c.c. of distilled water. Comparison of the coloration thus obtained with the standard colour solutions gives the amoimt of nitre in the liquid and consequently in the substance tested.

If the colour obtained is deeper than that of any of the standard liquids, the liquid tested must contain more than o*ooi gram of nitrate per 10 c.c. ; it should then be suitably diluted with distilled water.

This method is rapid and gives results sufficiently exact for practical pur- poses.

(c) Boric Acid. For the qualitative test, 10-20 grams of the sample are incinerated in the usual way after addition of a few c.c. of 20% sodium carbonate solution. The carbon-free ash is treated with 5 c.c. of hydro- chloric acid diluted to 10% and the solution poured into a test-tube, into which also the dish is washed with 15 c.c. of 95% alcohol. 15 c.c. of cone, hydrochloric acid (D 1-19) are then added and the well-cooled mixture


shaken with o-2 c.c. of a o-i% curcumin solution ^ and left at rest in the dark for half an hour, after which the colour of the liquid is observed. In presence of boric acid, this varies from faint brown (minimal traces of the acid) to pink or red ; in absence of boric acid the liquid remains yellow.

The quantitative determination is carried out colorimetrically in the same way with a weighed quantity of the sample. The coloration of the liquid is compared (as in estimating potassium nitrate) with a series of tubes in which solutions containing definite proportions of boric acid (O'l, o-2» 03, etc., %) are treated with the same amounts of acid, alcohol and curcumin solution in each case.

This method is rapid and fairly exact. With products containing much Salt, the latter settles at the bottom of the tube after treatment with alcohol and hydrochloric acid, but such deposit has no influence on the judging of the colours.

(d) Formaldehyde. This may be detected by one of the two following tests :

(i) 5 grams of the sample are thoroughly shaken in a beaker with 10 c.c. of hot water, the mass being filtered through a cloth and well pressed. A granule of phenylhydrazine hydrochloride is dissolved in 5 c.c. of the filtrate and the solution then treated with three or four drops of 5% sodium nitroprusside solution and ten drops of 10% caustic soda solution. In presence of formaldehyde a more or less intense blue coloration is observed, this remaining unchanged for some time {Rimini's reaction)}

(2) 50 grams of the sample are mixed with an equal weight of 20% phosphoric acid solution and the mixture distilled imtil about 30 c.c. of distillate are collected. To this is added about o-i gram of peptone,' and to 10 c.c. of the liquid are then added a drop of 5% ferric chloride solution and, carefully, 10 c.c. of cone, sulphuric acid. In presence of formaldehyde a dark violet ring is formed, and, when shaken, the liquid becomes violet if the amoimt of formaldehyde is marked, or reddish-violet if the amount is very small.

(e) Sulphur Dioxide and its Derivatives. In considerable quantity, sulphur dioxide is detectable by the smell. Otherwise it may be detected as follows :

About 50 grams of the sample are mixed intimately in a flask with 10 c.c. of 25% phosphoric acid. The flask is then closed with a cork, between which and the neck of the flask is placed a strip of starch-iodide paper moistened at the lower end, which is adjusted so as to be about i cm. from the meat. If the paper exhibits no coloration in the course of a few minutes the flask is heated in a water-bath imtil it attains the temperature of the

* The curcumin may be prepared as follows : 30 grams of turmeric powder (Cur- cuma longa) are dried at 100° and then treated for four hours in an extraction apparatus with petroleum ether. The dry, defatted powder is then extracted in the same appara- tus with 100 c.c. of benzene for 8-10 hours ; on cooling, the benzene solution deposits the curcumin as a fine, yellowish, crystalline powder.

To prepare solutions or curcumin paper, o-io gram of the turmeric is dissolved in 100 c.c. of 90% alcohol.

* Ann. di farmacoterapia e chimica, 1898, No. 3.

* Fresh milk, quite free from formaldehyde, may also be used ; in this case 30 c.c. of the milk are added to the distillate, the subsequent procedure being as above.


latter, and is then allowed to cool. If a blue coloration of the paper develops after half an hour, the presence of sulphur dioxide, sulphite or bisulphite is assumed.

When the qualitative test gives positive results and a quantitative deter- mination is required, the procedure is as follows :

50 grains of the meat are mixed to a paste with 100 c.c. of boiled water and 20 c.c. of 25% phosphoric acid added. The flask is closed with a two-holed stopper through which pass (i) a tube dipping into the Uquid and serving for the passage of a current of carbon dioxide, and (2) a tube connected with a condenser which dips, at the far end, below the surface of 100 c.c. of a solution of iodine in potassium iodide.^ About one-half of the liquid is distilled and the distillate acidified with hydrochloric add and precipitated with barium chloride in the usual way : i gram of BaS04 = 02748 gram of SO,.

(/) Fluorides. 25 grams of the sample, weighed in a platinum dish, are mixed with a certain amount of milk of lime, dried on a water- bath and incinerated ; the ash is introduced into a small platinum crucible and moistened with a few drops of water and then i c.c. of cone, sulphuric acid. The crucible is covered with a watch-glass coated on the lower surface with wax, which is partially scraped away ; the crucible is then heated in an asbestos card and the glass examined to see if it is etched at the exposed places.

(g) Salicylic Acid. 10 grams of the meat are well shaken with 20 c.c. of alcohol and, after a few minutes, filtered, a few drops of dilute ferric chloride solution being added to the filtrate : a reddish-violet coloration indicates salicylic add or one of its derivatives.

If a doubtful result is obtained, as may be the case when the salicylic acid is in very small quantity, the test is repeated as follows : * About 50 grams of the meat are weighed in a beaker and mixed with sufficient 2% sodium carbonate solution to give a homogeneous paste. After