AGBICULTUEAL CHEMISTEY — -AGROTECHNY. 211 



or the color of coffee with cream in it, is obtained. Stand a few moments; 

 then check the action of acid with 5 cc. of cold water with shaking. (This 

 should be done before the solution becomes a deep dark brown or blackish 

 color, which shows charring action on the sugar, which precipitate, if formed, 

 is difficult to dissolve.) 



" The solution having the color of coffee with ci-eam in it, centrifuge 5 

 minutes; then add 5 cc. of boiling water, whirl one-half minute longer. Drain 

 off the acid through the glass stopcock carefully by tilting the bottle (ap- 

 proximately 5 cc. of solution will be left). Dilute with cold water up to 10 cc. 

 and shake; add acid in small portions as above, with shaking (approximately 

 8 to 10 cc.) until the remaining curd is dissolved or an almost coffee-black 

 color, as in testing milk, is obtained. Add 3 cc. excess of acid and shake. 

 Whirl 4 minutes; dilute to the neck with an acid solution, 3 parts of the sulphuric 

 acid to 5 of water, at a temperature of about GO to 70° C. Whirl 1 minute; 

 theu add boiling water up to zero or above and again whirl 1 minute more. 

 Read the percentage of fat." 



The results obtained were on the average O.G per cent low. •" The percentage 

 of residual fat in the drained portion averages the same as that lost in 

 cream testing. The maximum variation in fat readings is not great considering 

 that the variation is somewhat greater on samples which have stood some time 

 and hence are not perfectly uniform. The variation with the modified Babcock 

 compares favorably with the Rose-Gottlieb method. This method can be used 

 in international centrifuges in food control laboratories if preferred, by using 

 a separatory funnel with a graduated cream tube at the top. This method 

 is also applicable to ice cream plants using the oi'dinary commercial sulphuric 

 acid on hand. Likewise, a similarly modified 10 per cent milk test bottle can be 

 used for determining fat in sweetened condensed milk." 



A rapid method for the determination of fat in ice cream, H. F. Lichten- 

 BERG (Jour. Indus, and Engin. Cliem., 5 (1913), No. 9, p. 786). — The method is 

 as follows : 



" Weigh into a 10 per cent Babcock milk bottle 9 gm. of melted sample. Add 

 20 cc. of glacial acetic acid (specific gravity 1.049). Mix well and add 10 cc. 

 of sulphuric acid (specific gravity 1.83). Mix again and proceed as in the 

 regular Babcock test. With the aid of a pair of dividers read the fat column 

 (from one extreme to the other; in other words, read the highest part of the 

 meniscus which appears as a straight line when the bottle is held on the level 

 of the eye and away from the source of light) at a temperature of 130° F. 

 The result times 2 equals the percentage of fat." 



A micro-chemical method for the determination of a- and /3-amino acids 

 and certain derivatives in proteolysis, bloods, and urine, P. A. Kober and K. 

 SuGiuRA {Jour. Amer. Chein. Soc, 35 (1913), No. 10, pp. 1546-1584) .—'' The 

 method (E. S. R., 26, p. 107) of forming copper complexes of amino acids, 

 peptids, and peptones in neutral or slightly alkaline solution (Ch = 10"^-°'^ to 

 10"*-^) has been improved so that quantitative results can be obtained in very 

 dilute solution (1 part in 500,000). The ' precipitability ' of the copper in the 

 complexes of 19 amino acids, 27 dipeptids, 18 tripeptids, and 4 tetrapeptids is 

 given, when in equilibrium with 0.06 normal Ba(0H)2, and it is shown that 

 the amount of copper dissolved by the free amino acid, as well as the amount 

 dissolved by the peptids and peptones, can be separately determined, thus 

 estimating these substances in micro-chemical mixtures. 



" Experiments are given to show that under the conditions of this method 

 \ery few other substances react with the reagent, and that these can easily be 

 removed without interfering with the estimation of amino acids and their 

 liomologues. The method is applied to proteolysis, blood, and urine, and it is 



