810 EXPEEIMENr STATION EBCOKD. 



Detection and estimation of the xanthin bases in cocoa, tea, coffee, and 

 their derivatives, S. Camilla and C. Pertusi (Ahs. in Jour. Cliem. Soc. 

 [London], 102 (1012), No. '601, II, p. 1111; Jour. Soc. Chem. Indus., 31 {1912), 

 No. 22, pp. 1002). — Small amounts of xanthin bases can be detected with 

 potassium permanganate and potassium hydroxid in an aqueous solution 

 wherein they form carbylamins. For estimating the xanthin bases, the follow- 

 ing procedure is recommended : 



Ten gm. of chocolate or cocoa is boiled for one-half hour with 150 cc. of water 

 and 50 cc. of normal sulphuric acid solution, made up to 500 cc. with water, 

 and then filtered hot. One-half of the filtrate is neutralized with magnesium 

 oxid, concentrate to about SO cc. on the water bath, acidify with dilute sul- 

 phuric acid, and extract with carbon tetrachlorid for from 2 to 3 hours. The 

 extract, which contains the caffein, small amounts of theobromin, and fat. is 

 after adding a little piece of paraffin, evaporated to dryness and the residue 

 extracted with boiling water acidified with sulphuric acid. The solution Is 

 filtered and added to the remaining half of the original extract, and the whole 

 evaporated to dryness with 5 gm. of magnesium oxid. The residue is ex- 

 tracted with boiling chloroform 4 or 5 times, using 100 cc. of solvent each time. 

 The chloroform solution is then evaporated. 



Tea and coffee products can be dealt with by n similar process. 



The Babcock test with special reference to testing cream, H. E. Ross and 

 T. J. MclNERNEY (Xew YovJc Cornell Sta. Bid. 337 {1913), pp. 21-lfi, figs. 12).— 

 This gives specific directions for performing the Babcock test for fat in milk, 

 cream, skim milk, butter, cheese, sour milk, and churned milk, with some results 

 of experiments. 



In those which were made for the purpose of determining the effect of tem- 

 perature on the fat column of a whole-milk bottle it was shown that " the fat 

 column in a whole-milk bottle is not large enough to be greatly affected by 

 temperature unless it is extremely hot or cold." 



In testing skim milk it is necessary to use a special bottle, extra acid, and to 

 whirl for a longer period of time in order to get proper results. Frozen milk 

 should be melted, but in melting the ice no temperature above 85° F. should be 

 used. Milk allowed to stand a time before freezing will show a high content of 

 fat in the ice,, while a milk agitated while freezing will show a greater quantity 

 of fat in the liquid part. 



For testing cream better results may be obtained by weighing the sample than 

 by measuring it. In the experiments a difference of 0.5 to 4.5 per cent was 

 noted between the two. It is advisable to immerse the cream bottle with its 

 contents, after treatment with acid, in a water bath at 150° and in such a man- 

 ner that the fat column is below the surface of the water. The length of time 

 necessary for the fat column to reach the temperature of the bath varied in 

 the experiments from 2 to 4 minutes. The use of about 0.5 cc. of glymol (white 

 mineral oil) colored with alkanet is recommended in order to facilitate the 

 reading of the fat column. This removes the meniscus and makes a sharper 

 line of demarcation between the fat column and the added substance. 



When the chemical method (ether extraction) is compared with the Babcock 

 method and the meniscus is removed with glymol, " the Babcock method will 

 compare very favorably for all practical purposes with the chemical method 

 when read at a temperature between 140 and 150°. Sixty-four experiments 

 were performed, both Babcock and chemical, and of that number there were 35 

 that compared within 0.2 per cent. The cream bottles are graduated only as 

 fine as 0.5 per cent; therefore it may be concluded that in this number of ex- 

 periments there were only 8 that varied more than 0.5 per cent." 



