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method is easier of manipulation and much quicker than the Stahlschmidt method and, at the same time, uses a sample three times as large.

Three samples of coffee-A, "caffein-free" coffee purchased on the market; B, Santos medium roast; and C, Rio medium roast-were ground to pass a 1 mm. sieve without residue, were thoroughly mixed and sent to twelve collaborators with the request that they be examined by the Stahlschmidt1 and the Fendler-Stüber methods. Although the latter method was tried in its original form, it is believed that an improvement tending to easier, quicker, and more accurate manipulation is

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*Purified by iodin method. U. S. Bur. Chem. Bull. 137: (1911), 191.

1 Assoc. Official Agr. Chemists, Methods, 1916, 332.

possible. It is suggested that the filtrate from the first chloroform extract be caught in a tared flask, with stopper, and the entire filtrate weighed to the nearest tenth of a gram, thereby eliminating the necessity of weighing 150 grams of volatile chloroform solution with the coincident concentration by evaporation. The results received from nine collaborators are submitted in Tables 2, 3 and 4.

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* Purified by the iodin method. U. S. Bur. Chem. Bull. 137: (1911), 191.

DISCUSSION OF RESULTS.

On pure coffee, Samples B and C, the Fendler-Stüber method, judging from the nitrogen determination, gives a purer caffein than the Stahlschmidt method and in all cases but one gives a percentage of alkaloid equal to that obtained by the other procedure. The results on the "caffein-free" coffee, Sample A, also show a purer caffein obtained by the Fendler-Stüber method but in all cases a slightly less amount. It is possible that, in the method of manufacture of this type of product, nitrogen-containing bodies are affected in a manner whereby they contaminate the crude residue of caffein in the Stahlschmidt method but are eliminated in the purification process of the Fendler-Stüber method. The analysts who commented on the methods were unanimous in their preference for the Fendler-Stüber method.

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* Purified by iodin method. U. S. Bur. Chem. Bull. 137: (1911), 191.

RECOMMENDATIONS.

In view of the concordant satisfactory results obtained by the collaborators and the many advantages of the Fendler-Stüber method, it is recommended

(1) That the Gorter method for the determination of caffein in coffee1 be dropped.

(2) That the Stahlschmidt method be not made official this year. (3) That the Fendler-Stüber method be adopted tentatively.

(4) That the Fendler-Stüber method be tried next year on other coffees, including raw coffee, with a view to its adoption as official.

1 Assoc. Official Agr. Chemists, Methods, 1916, 332.

REPORT ON TEA.

By E. A. READ (Bureau of Chemistry, Washington, D. C.), Referee.

According to the 1916 annual report of the supervising tea examiner of the Treasury Department practically no colored tea (0.00197 per cent) was offered for entry into this country during that year. The problems in connection with adulteration could be well included under microscopical methods, otherwise, the examination of tea seems to be entirely chemical. It is therefore suggested that the subjects, coffee and tea, be combined as in previous years and assigned to a chemist as referee.

REPORT ON BAKING POWDER.

By. H. E. PATTEN1 (Bureau of Chemistry, Washington, D. C.), Referee.

Following the recommendations of the referee for 1916, a further study of the Wichmann, and of the newly proposed Chittick, and CorperBryan methods for the determination of lead in baking powder has been conducted. The results obtained in 1916 demonstrated that none of the available methods for lead was satisfactory. Consequently, the collaborators were advised to vary conditions, make preliminary runs and do independent research, as well as to analyze samples of baking powder containing known quantities of lead.

In addition to the work on lead, collaborators have greatly improved the method of determining fluorin, so that it is now possible to present a rapid, accurate method of great range as to quantity determined which has the added value that silico-fluorids, as well as fluorids, give up their fluorin.

In connection with the lead investigation, experiments were made to determine the hydrogen ion concentration at which calcium citrate is held back from rapid precipitation in so-called neutral ammonium citrate solution, which is of general analytical interest, as well as the hydrogen ion concentration at which lead sulphid is precipitated, and the iron held up in solution under the conditions of the Wichmann modification of the Seeker-Clayton method.

1 Present address, Provident Chemical Works, St. Louis, Mo.

WORK ON COLLABORATIVE SAMPLES.

The samples were made up in 100 pound lots from standard baking powder ingredients as used in the trade, and the lead when added was in the form of lead sulphate. The proportions of ingredients and kinds of baking powder making up the various samples are given in Table 1.

TABLE 1.

Data on preparation of collaborative samples of baking powder.

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1712

Sodium aluminium sulphate baking 2.656 grams of lead sulphate per 80 powder + known lead.

pounds

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=

50 parts per million

27

.21

8

44

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Sodium aluminium phosphate.
Phosphate..

Starch.

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It will be noted that Nos. 1701, 1711 and 1721 are the samples containing no added lead. Their lead content was obtained by analysis. The lead added amounted to 50 parts per million parts of baking powder, calculated as metallic lead.

NOTE: In the following methods, lead-free reagents must be used.

Gravimetric Method for the Determination of Lead in Baking Powder.

(Proposed by J. R. Chittick, Jaques Manufacturing Company, Chicago, Ill.)

PREPARATION OF REAGENTS.

Sulphuric acid (1 to 5).-Mix 500 cc. of 95% sulphuric acid, C. P., with 2500 cc. of water, let stand overnight, and filter.

Acid-alcohol-water mixture.-Mix 80 cc. of 95% sulphuric acid, C. P., with 3000 cc. of water. Then add 800 cc. of redistilled 95% alcohol (methyl or ethyl), stir thoroughly, let stand overnight, and filter.

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