804 EXPERIMENT STATION RECORD. . [Vol. 37 



to unknown mixtures it is necessary to establish that not more than three 

 acids are present in significant quantities. This fact established, a distilla- 

 tion by the Duclaux method should suffice for both qualitative and quantitative 

 analysis of the mixture. The methods of calculation do not depend on the 

 form of the laws governing the rates of distillation of pure acids in aqueous 

 solution, and therefore do not necessarily depend on the mode of distillation. 

 The calculations may therefore be applied to distillations made in other ways, 

 for instance, to steam distillations at constant volume. It is merely necessary 

 to conduct all distillations both of pure acids and of mixtures in the same 

 manner." 



A modification of the McLean- Van Slyke method for the determination of 

 chlorids in blood, G. L. Foster {Jour. Biol. Chcni.. 31 (1917), .Yo. 5, pp. J,83- 

 485). — The method previously described (E. S. R., 34, p. 507) has been modified 

 in that a freshly prepared 25 per cent solution of metaphosphoric acid is used 

 for coagulating the proteins. The procedure is described as follows : 



To 2 cc. of the sample in a 25-cc. volumetric flask, 20 cc. of water is added 

 and then slowly, with stirring, 1 cc. of a freshly prepared solution of meta- 

 phosphoric acid. The flask is filled to the mark, well shaken, and allowed to 

 stand for ten minutes with occasional agitation. The contents of the flask are 

 then filtered and 10 cc. of the filtrate used for the determination, as described 

 in the original method. 



Studies of acidosis. — II. A method for the determination of carbon dioxid 

 and carbonates in solution. D. D. Van Slyke (Jour. Biol. Chem.. 30 (1911), 

 No. 2, pp. S47S68, figs. 4). — A simple one-piece apparatus for the determination 

 of carbon dioxid or carbonates in water solutions and ita manipulation are de- 

 scribed. 



The principle of the method is that of vacuum extraction. The apparatus 

 was designed especially for analysis of 1-cc. samples of blood plasma, but is 

 indicated as being applicable to aqueous solutions in general, as well as for 

 the determination of dissolved gases other than carbon dioxid. A mlcroap- 

 paratus with which the carbon dioxid content of 0.2 cc. of plasma can be de- 

 termined with an accuracy of one volume per cent, designed on the same prin- 

 ciple, is also described. The entire analysis Is performed at room tempera- 

 ture and requires only about three minutes. 



The calculation of the results is described In detail. 



Methods for the determination of saccharin in food products, A. Bonis 

 (Ann. Falsif., 10 (1917), No. 103-10^, pp. 210-218).— A general review of the- 

 procedures for extracting saccharin and purifying the residue, and of methods 

 of identiflcation and quantitative determination. 



Application of the cryoscopic method for determining added water in milk, 

 J. T. Keisteb (Jour. Indus, and Engin. Chem., 9 (1917), No. 9. pp. 862-865).— 

 It is concluded from the study that " the freezing-point figure of milk is the 

 most constant one yet obtained and the safest basis upon which to draw con- 

 clusions as to the presence or absence of added water." Water added to fresh 

 milk in excess of 5 per cent was detected with certainty by the freezing-point 

 method. The use of sufficient formaldehyde for preservation was found to lower 

 the freezing point. The test should be applied to the milk before any marked 

 increase in acidity has taken place, since Increased acidity affects the final re- 

 sults. 



The freezing-point figures of the milk of 16 Individual cows are submitted in 

 tabular form, and the apparatus for determining the freezing point and its 

 manipulation are described. 



