A brief review of the methods that have been used or recommended for the analysis of cocoa and its preparation is here given. If any important recently reported methods have been omitted, it is due to a greatly regretted and unintentional oversight.

Preparation of the sample. - The method of analysis adopted by the Association of Swiss Analytical Chemists3 directs that the substance should always be finely powdered or rasped, and kept in well-stoppered bottles. Bensemann4 prepares the beans by grinding in a porcelain mortar, separates the husk by use of a knife, and scrapes chocolate with a knife to prepare it for analysis. Mansfeld1 recommends that the material be finely rasped or powdered.

1 Op. cit., note 3, p. 940 of this work.

2 Mace, Les substances alimentaires etudiees au microscope.

3 Vicrteljahresschrift ii. d. Fortschritte auf d. Gebiete d. Chem. d. Nahr. u. Genusa-mittel, 1890, 2, 171.

4 Rep. f. anal. Chem., 1884, 4, 213.

Determination of moisture. - The Association of Swiss Analytical Chemists 2 makes this determination in cocoa powder. Two grams are spread in a thin layer on a watch glass and dried to constant weight at 105° C. Bensemann3 dries 2 grams to a constant weight at 100° C.; Herbst,4 a weighed quantity, mixed with twice its weight of sand, at 60° to 80° C.; Mansfeld,1 5 grams to constant weight at 100° C.

Quantitative and qualitative examination of the ash. - For quantitative determination, the method of the Association Swiss Analytical Chemists2 directs that the material be incinerated in a platinum dish, carefully burned at a low red heat until the ash is white, and after moistening with (NH4)2C03, gently reignited. The ash is also examined qualitatively for mineral substances and pigments; as ocher, bolus, excess of alkaline carbonates used in making the cocoa soluble, etc.

Bensemann.3 - Two grams of material are carbonized, extracted with water, and the residue washed and incinerated. The aqueous extract is added to the ash and the whole evaporated to dryness. The residue is dried at 100° C, weighed, and the result taken as ash. All ashes were of a light gray, almost white, color, so that the addition of ocher, bolus, etc., could be easily detected by a red color of the ash.

Mansfeld1 burns 5 grains at a low temperature and tests the ash for mineral additions; as ocher, excess of alkaline carbonates, etc.

Stutzer5 mixes 2 grams with sand, incinerates at a moderate heat, adds NH4N03, and ignites again until the ash is white and free from C02 and nitrates. In a recent article6 this writer has called attention to the value of the additional determinations of ash soluble in water, total P2O5 and P205 soluble in water, as a means of detecting the use of fixed alkalis and ammonia in the process of manufacture. His results are given in the table on page 943.

Quantitatived etermination of fat. - Association of Swiss Analytical Chemists.2 - The sample is mixed with sand, extracted with absolute ether in a Soxhlet apparatus for six to eight hours; the ether is removed by careful evaporation, and the fat dried at 100° C.

Bensemann.3 - Two grams of the substance are rubbed to a powder in a mortar warmed to 60° C, some gypsum being added to facilitate the pulverizing. The mass is extracted with ether in a Soxhlet apparatus and the extract is dried at 100° C.

Blyth.7 - The best method of extracting the fat is to exhaust the nibs with ether in a Soxhlet apparatus.

Boussingault.8 mixes the material with sand and extracts with carbon disulphide.

Hassall.9 - Three grams of cocoa are dried in the water bath and exhausted with ether; the ether is evaporated off, and the residue dried and weighed. This residue contains some or all of the theobromine, the amount of which must be determined and subtracted from the ether extract.

Herbst.4 - The residue from the moisture determination "is extracted with ether and the extract dried at 100° C.

1 Zeitschr. d. allgem. osterr. Apotek. Ver., 44, 329.

2Vierteljahresschrift ii. d. Fortschritte auf d. Gebiete d. Chem. d. Nahr. u. Genus-smittel, 1890, 2, 171. 3 Rep. f. anal. Chem., 1884,4, 213.

4Rundschau, 1882, 443; Rep. d. anal. Chem., 2, 236; Zeitsch. f. anal. Chem., 22,278. 5Rep. f. anal. Chem., 1882, 88 and 165; Hygiene-Bericht, 1882-'3, 1, 217. 6 Op. cit., note 3, p. 939 of this work.

7 Op. cit., note 3, p. 936 of this work.

8 Ann. Chem. Phys., [5], 28, 433; Jour. Chem. Soc, 1884, 46, 202; Chem. Ztg., 1883, 203, and 902.

9 Op. cit., note 2, p. 940 of this work.

Mansfeld.1 - Five grams of cocoa, or 10 grams of chocolate, are mixed with an equal weight of sand and extracted in a Soxhlet apparatus with petroleum ether.

Wolfram 2 uses petroleum ether for the extraction of the fat.

Qualitative examination of the fat.3 - The Association of Swiss Analytical Chemists4 recommends the determination of the melting point by Ruhdorf's method, Hubls' iodine number, and Kottstorfer's saponification number. Bjorklund's ether test and Filsinger's ether-alcohol test are also stated to be of value.

Bjorklund5 covers about 3 grams of the fat in a test tube with double its weight of ether, closes with a cork, and tries to bring the mass in solution by shaking at 18° C. When wax is present, a cloudy solution results, which is not changed by warming. If the solution is clear, the tube is placed in water at 0° C. and the time observed after which the solution begins to become milky or to deposit white flakes; then the temperature is noted at which the mixture becomes clear on removing from the water. When the solution becomes cloudy after ten to fifteen minutes and at 19° to 20° C. is again clear, the cocoa butter is pure. For a cocoa butter containing 5 per cent of beef tallow, these numbers are eight minutes and 22° C.; 10 per cent tallow, 7 minutes and 25° C, etc.