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TREATISE ON
APPLIED ANALYTICAL CHEMISTRY



TREATISE ON

APPLIED ANALYTICAL

CHEMISTRY

METHODS AND STANDARDS

for the Chemical Analysis of the Principal
Industrial and Food Products

By
PROFESSOR VITTORTO VILLAVECCH1A

Director of the Chemical Laboratories of the Italian Customs

WITH THE COLLABORATION OF

G. FABRIS A. BIANCHI G. ARMANI

G. ROSSI G. SILVESTRI G. BOSCO

R. BELASIO F. BARBONI A. CAPPELLI

TRANSLATED BY

THOMAS H. POPE, B.Sc., A.C.G.I., F.I.C.

University of Birmingham



VOL. II.

WITH 105 ILLUSTRATIONS IN THE TEXT



PHILADELPHIA

P. BLAKISTON'S SON & CO.

1012 WALNUT STREET

1918



Printed in Great Britain



TRANSLATOR'S NOTE

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 country.

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.



vn



CONTENTS



PAGE

CHAP. I. Meat and its Preparations ....... i

Meat I

Sausages ........... 3

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

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

CHAP. II. Milk 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 Ilf. 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 17-5 C. . 91

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

Refracto metric 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

ix



x CONTENTS

PAGE

Table XII. Glucose corresponding with copper reduced (Allihn) no
Table XIII. Invert sugar corresponding with copper reduced

(Meissl) in

Table XIV. Maltose corresponding with copper reduced (Wein) in

Table XV. Lactose corresponding with copper reduced (Soxhlet) 112

Table XVI. Constants of the principal sugars . . .113

Determination of the sugars in their mixtures . . . .114

Special Part ........... 122

Prime materials and products of the sugar industry . . .122

Beet . 123

Diffusion juices ......... 126

Defecated juices . . . . . . . . .129

Dense juice and syrup ........ 129

Massecuite 131

Molasses ........... 132

Raw sugars 133

Table XVII. Invert sugar corresponding with copper (Herzfeld) 136

Table XVIII. Factors for the calculation of invert sugar . 136

Refined sugars. . . . . . . . . . 139

Exhausted slices . . . . . . . . .140

Waste and wash waters . . . . . . . . 140

Filter-press sludge . . . . . . . . .140

Other sugars . . . . . . . . . 141

Glucose .......... 141

Maltose ........... 143

Invert sugar .......... 145

Products containing sugars . . . . . . . M5

Crystallised and candied fruits . . . . . . .145

Preserved fruit ......... 149

Jams 149

Chocolates .......... 152

Sweetmeats .......... 156

Jujubes 156

Biscuits and milk flour . . . . . . . .157

Marzipan. .......... 158

Citrate of magnesia . . . . . . . . .158

Honey ........... 159

CHAP. V. Beer 164

Specific gravity . . . 164

Original gravity and alcoholic strength . . . . .165

Table XIX. Original gravity table . . . .165

Table XX. Correction of spirit indication for acidity . 166
Determination of ash . . . . . . . .166

,, chlorides ....... 167

acidity . . . . . . . 167

carbon dioxide . . . . . .168

glycerine ....... 168

maltose 168

,, dextrin ....... 169

nitrogenous substances . . . .169

Detection of antiseptics . . . . . . .169

artificial sweetening agents . . . -171

extraneous bitter substances . . . -17*
injurious metals . . . . . .172

pasteurisation . . . . . . .172



CONTENTS xi

PAGE

Forcing test ......... 172

Determination of arsenic . . . . . . 173

CHAP. VI. Wine 175

External examination . . . . . . . .176

Specific gravity . . . . . . . . .177

Alcohol content . . . . . . . . 177

Table XXI. Alcohol table 179

Extract 182

Table XXII. Extract table . .... 184

Determination of ash . . . . . . . .189

alkalinity of the ash . . . . .190

,, acidity ....... 191

tartaric acid 193

sugars . 194

Detection of dextrin and impure glucose .... 196

Determination of the glycerine ...... 197

Measurement of the colour ...... 199

Detection of extraneous colouring matters .... 200

Determination of the sulphates ...... 203

chlorides ...... 204

Investigation of the nitrates ....... 205

Determination of the phosphoric acid ..... 206

Detection of citric acid ........ 208

,, free mineral acids ...... 208

Table XXIII. Values of a : b 211

Detection and determination of antiseptics . . . .211

Detection of artificial sweetening agents . . . .215

,, and determination of extraneous metals . .217

Microscopic examination . . . . . . .219

Vinegar ........... 222

CHAP. VII. Spirits and Liqueurs ....... 229

General methods .......... 230

Objective characters ........ 230

Determination of alcohol ....... 230

Table XXIV. Alcoholic strength from specific gravity . 234

Determination of the extract and ash . . . . .238

Detection and determination of impurities .... 238

Table XXV. Dilution of alcohol to 90% strength . . 238
Table XXVI. Strengthening of dilute spirit to 50% con-
centration by means of 90% alcohol .... 240

Table XXVII. Dilution of strong alcohol to 50% concentra-
tion .......... 241

Determination of the acidity. ...... 243

,, ,, esters ....... 243

Detection and determination of the aldehydes . . . 244

,, furfural .... 246

Determination of the higher alcohols ..... 246

Detection and determination of metals ..... 250

denaturants .... 251

,, ,, methyl alcohol . . .258

Special part ........... 260

Industrial spirit .......... 260

Table XXVIII. Composition of industrial spirits , . 261



xii CONTENTS

PAGE
Fusel oils .......... 261

Eau-de-vie .......... 262

Table XXIX. Compositions of eaux-de-vie . . . 263

Cognac ........... 263

Table XXX. Compositions of cognacs . . . .265
Rum ........... 265

Table XXXI. Compositions of genuine rums . . .266
Fruit spirits .......... 266

Table XXXII. Compositions of fruit spirits . . . 269
Cereal spirits . . . . . . - . . . . 269

Table XXXIII. Compositions of whisky and gin . .270
Liqueurs ........... 270

CHAP. VIII. Essential Oils 274

General methods .......... 274

External characters . . . . . . . -275

Determination of the specific gravity 275

,, ,, rotatory power . . . . -275

,, ,, refractive index . . . . .276

,, ,, solidifying point . . . . -277

,, boiling point ..... 278

solubility 278

esters . . .279

,, free alcohols ..... 280

aldehydes 281

phenols . . . . . 282

Special investigations . . . . . . . .282

Special part 285

Bitter orange oil . . . . . . . .285

Sweet orange oil ......... 285

Bergamot oil ......... 286

Oil of lemon 289

Other essential oils 298

Table XXXIV. Characters and compositions of the com-
moner essential oils .... . 292

CHAP. IX. -Turpentine and its Products 299

Turpentine .......... 299

Oil of turpentine . 301

Colophony . . . . . . . . . 306

Resin oils 309

CHAP. X. -Varnishes 3 J 3

Practical tests 313

Chemical analysis . . . . . . . . -314

Table XXXV. Densities and boiling points of solvents for

varnishes 317

Table XXXVI. Characters of solvents for varnishes . -317

CHAP. XI. Rubber and Guttapercha 321

Raw and purified rubber . . . . . . 321

Factis 324

Vulcanised and manufactured rubber ..... 325

Ebonite .329

Guttapercha ,../.. 329



CONTENTS xiii

PAGE

CHAP. XII. Tanning Products . 33 1

Prime materials and tanning extracts . 331

Qualitative examination . 33 x

Table XXXVII. Reactions of tanning substances . . 334

Quantitative analysis . -337

Table XXXVIII. Compositions of tanning materials . . 346

Tannin . 34 6

CHAP. XIII. Inks 34

Qualitative tests .... . 34 8

Quantitative analysis . ^ 35 2

Practical tests . . . . . -. -353

CHAP. XIV. Leather 355

Tanned leather 355

Physical and mechanical tests 355

Chemical analysis . . . . . . . -357

Table XXXIX. Compositions of various sole leathers . 362

Chromed leather ......... 364

Physical and mechanical tests ...... 364

Chemical analysis . 364

CHAP. XV. Colouring Matters . , 366

Mineral colours (pigments) ........ 366

General methods .......... 366

Technical tests . . . . . . . . .366

Chemical analysis . . . . . . . -370

Special part ........... 372

White pigments ......... 372

Table XL. Scheme for the recognition of white pigments . 373

White lead 372

Zinc white 375

Lithopone .......... 377

Permanent white . . . . . . . . -378

Red and yellow pigments . . . . . . . 379

Table XLI. Scheme for the recognition of red and yellow

pigments . . . . . . . . . 380

Chrome yellow, Chrome red . . . . . . -379

English red .......... 381

Ochres ........... 383

Minium ........... 384

Cinnabar, Vermilion ........ 386

Cadmium yellow ......... 387

Green and blue pigments . . . . . . . .388

Table XLI I. Scheme for the recognition of blue and green

pigments ......... 389

Ultramarine .......... 390

Prussian blue, Turnbull's blue ....... 392

Greens and blues with a copper basis 393

Chrome green .......... 395

Mixed chrome greens ........ 395

Terre verte .......... 396



xiv CONTENTS

PAGE

Brown, grey and black pigments 396

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

black pigments ........ 397

Umber -398

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

Graphite . . -399

Black pigments with a basis of carbon ..... 400

Metallic pigments . . . . . . . . .401

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 411

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

Alizarin . 4 l6

Catechu, Gambier . . . . . . . . .419

Cochineal .... .420

Carmine .......... 421

Artificial organic colouring matters . . . . . .422

Identification of colouring matters 424

Table XLIV. Basic and basic mordant dyestuffs . .427
Table XLV. Salt and sulphur dyestuffs . . . .428
Table XLVI. Acid and acid mordant dyestuffs . . . 430
Table XLVII. Dyestuffs 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, Yarns, Fabrics . - 44 1

Microscopic examination . . 44 1

Table LII. Microscopic characters of vegetable fibres. . 445

Table LIII. Microscopic characters of animal fibres . . 451

Chemical examination . . . . . - -455

Tables LIV, LV, LVI, LVII, LVIII, LIX, LX. Id?ntification

of colouring matters on wool 477

Tables LXI, LXII, LXIII, LXIV, LXV, LXVI, LXVII.

Identification of colouring matters on cotton . . 497

Physico-mechanical examination . . . . . 5 2 ^

INDEX jo THEjTwo VOLUMES t . , . . . . 5 2 9



CHAPTER I
MEAT AND ITS PREPARATIONS

MEAT

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

A.C. II, 1 1



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 until 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 grarr.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
being then filtered through paper until clear,



SAUSAGES 3

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 10 c.c. of 10% 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 i %) but no change in the nitro-
genous substances and fat.

SAUSAGES

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; Wocfonschrift f. Chem. u. Pharm,, 1910, XLVJII, p. 481.



4 SAUSAGES

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 c.c. ;

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,

4-5*

ga.

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 follows :

(a) According to Feder, 1 the presence of casein is shown by a high pro-
portion of lime in the ash, defatted meat containing only o '06-0-13% 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.

(b) 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 8-1 c.c. of normal acid, the addition of i% of
commercial albumin increases it to 20 c.c.

5. Detection and Determination of Starch. (a) Qualitative test. 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 liquid examined
under the microscope. A little iodine solution is then added and the speci-
men again examined microscopically for stained starch granules.

(b) Quantitative determination. 2 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 liquid is made up to 200 c.c., allowed to settle thoroughly, and
50 c,c, of it acidified in a beaker with acetic acid and treated with an equal

* Zeitschr. Unt. Nahr- und Genuss-mittel, 1909, XVII, p. 191.

* Mayrhofer ; Forschungsber,, III, 1896, pp. 141, 429.



SAUSAGES 5

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,



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