412 EXPEBIMENT STATION RECORD. 



The experimental data indicate that percentage concentrations of sodium 

 chlorid as low as 0.0156 interfere with the test. 



In determining the delicacy of Barfoed's test it was found that with 1 cc. 

 of the reagent, and heating for two minutes in boiling water, a concentration 

 of 0.08 per cent of glucose gave a very definite reduction, and that one-half 

 the concentration gave a faint reduction. The greenish-white precipitate was 

 formed by the action of sodium chlorid (concentration of 0.32 per cent) on 

 Barfoed's reagent at room temperature. Glucose has the same effect in the 

 presence of sodium chlorid at room temperature. The precipitate contains 

 copper, sodium, chlorin, and the acetic acid radical. When formed at room 

 temperature it tends to go into a colloidal solution. Its percentage composi- 

 tion was not determined. 



The quantitative determ^ination of the amino acids of feeding stuffs by the 

 Van Slyke method. — II, H. S. Grindley, ^I. E. Slater, et al. {Jour. Aiiicr. 

 Chem. Soc, 37 {1915), No. 12, pp. 2762-2769).— Results 'of the distribution of 

 the nitrogen of blood meal, wheat, rolled wheat, barley, oats, and white soy 

 beans are reported, together with those previously noted (E. S. R., 33, p. S05). 



The results reported "confirm the conclusion previously drawn, namely, that 

 the Van Slyke method for the determination of the chemical groups characteris- 

 tic of the amino acids of proteins can be applied directly to the quantitative 

 determinations of the amino acids of feeding stuffs with at least a fair degree 

 of accuracy." Pronounced variations in the free and combined amino-acid 

 content of the common feeding stuffs, expressed in percentage of the total 

 nitrogen and in percentage of the feeding stuffs, are indicated by the results 

 reported. The high results for humin nitrogen obtained are deemed probably 

 due in part to the presence of soluble carbohydrates during the hydrolysis of the 

 protein.s, and probably also to the presence of cellulose which mechanically pre- 

 vents a complete hydrolysis of the material. These high results for humin 

 nitrogen constitute a source of error in the direct application of the metliod 

 to the determination of the free and combined amino acids and amids of feeding 

 stuffs. 



See also a previous note by Nollau (E. S. R., 33, p. 6G.5). 



The nephelometric estimation of purin bases, including uric acid, in urine 

 and blood, Sara S. Graves and P. A. Koiier {Jour. Aincr. Chew. Soc, 37 {1'.>1.')), 

 Xo. 10, pp. 2.}.]0-2.}.'/7, fio^^- 3). — The authors have so modified Salkowski's 

 reagent for purin bases as to make it applicable to nephelometrical work. 

 They have found that the reagent will precipitate xanthin, hypoxanthin, guanin, 

 adenin, and uric acid quantitatively in solution as dilute as 0.0002 per cent. 

 The use of a clear solution of egg albumin as a protective colloid to keep the 

 precipitates in suspension has been introducetl. A suspension of manganese 

 dioxid in alkaline rather than acid medium was found to oxidize uric acid 

 completely in from one to three minutes and not attack the other purins. They 

 conclude that lu-ic acid and other purin bases in urine may be quickly and 

 fairly accurately estimated with the nephelometer. An outline of the technique 

 for the estimation of purin bases in blood is given. 



The use of ammonium hydroxid for the extraction of rosin from wood, 

 II. K. Benson and II. N. Crites {Jour. Indus, and Engin. Chcm., 7 {1915), No. 

 11, pp. 918-920, fig. 1). — By the treatment of resinous woods with an amount of 

 5 per cent ammonium-hydroxid solution equal to eight times the weight of the 

 wood, at 70° C. for five hours, an almost complete extraction of rosin was 

 obtained. From the general properties of ammonia it is believed that a complete 

 recovery of ammonia is possible. 



