310 EXPERIMENT STATION EECORD. 



New modification of the Kjeldahl method, I^. Marino and F. Gonnelli 

 {AtH R. Accctd. Lincei, Rend. CI. Sd. Fis., Mat. e Nat., 5. ser., 23 (1914), I, 

 No. 7, pp. 523-580; ahs. in Jour. Chem. Sac. [London'], 106 {19U), No. 621, 

 II, pp. 575, 576). — When vanadium pentoxid was used as a catalyst in the 

 Kjeldahl process, according to the suggestion of Oefele (see above), an error 

 of about 1 per cent Avas noted. Accurate results may be obtained, however, if 

 1 gm. of the organic substance is boiled with 20 cc. of concentrated sulphuric 

 acid, 7 gm. of potassium sulphate, and 0.2 gm. of vanadium pentoxid until an 

 emerald green colored solution is obtained. The method can be used to ad- 

 vantage in cases where the Gunning modification of Kjeldahl's method does not 

 suffice to convert tbe nitrogen into ammonia. 



About the decomposition of large amounts of organic substances accord- 

 ing to the Kjeldahl method, E. Caupiaux {Bui. Hoc. Chim. Belg., 27 (WIS), 

 No. 12, pp. 333, 33Jt; ahs. in Chem. Ztg., 38 {19H), No. 26, Repert., p. llJf). — 

 Usually as little as 5 gm. of substance is hard to oxidize in the Kjeldahl flask, 

 even with boiling sulphuric acid. The method utilized by the author for the 

 oxidation of from 20 to 30 gm. of organic substance is as follows : About 30 gm. 

 of the substance to be examined is placed in a Kjeldahl flask with about the 

 same amount of sulphuric acid, agitated thoroughly, and allowed to stand for 

 about one hour. If at the end of this period the mass is dry enough, there are 

 added mercury and enough sulphuric acid for oxidation, which is completed in 

 a few minutes. Although large amounts of sulphuric acid affect the nitrogen 

 £ind phosphoric acid, injury may be prevented by the addition of sugar. In the 

 resulting solution nitrogen, phosphoric acid, and calcium can easily be deter- 

 mined. 



A simplification of Bang's micro-Kjeldahl method and the protein content 

 of the vitreous humor of rabbits' and dogs' eyes, M. Kochmann {Biocliem. 

 Ztschr., 63 (1914), No. 4-6, pp. 479-482). — Bang's method ^^ consists of placing 

 100 mg. of blood in a 50 cc. Kjeldahl bottle with 1..5 cc. of pure sulphuric acid, 

 3 to 4 drops of 10 yter cent copper sulphate solution, and 2 pieces of iwtassium 

 sulphate about the size of a millet seed, and heating on a wire gauze until the 

 decomposition is complete. After cooling, 10 cc. of distilled water is added, 

 then 10 cc. of 20 per cent potassium hydroxid, the mixture cooled, and 10 cc. 

 more of potassium hydroxid solution added. The Kjeldahl flask with its con- 

 tents is then connected to the Bang distillation apparatus, which consists of 

 an expanded tube plugged with a wad of glass wool for the purpose of pre- 

 venting the passage of potassium hydroxid over into the distillate during dis- 

 tillation. This tube is connected at its lower end to the Kjeldahl bottle with a 

 perforated rubber cork, and at its upper end with a bent quartz tube which 

 contains at its outlet a small copper condenser. The distillate is collected in a 

 50 cc. beaker containing from 3 to 10 cc. of centinormal hydrochloric acid solu- 

 tion. The hydrochloric acid not neutralized by the ammonia is determined by 

 titration with centinormal thiosulphate solution, after adding starch paste, a 

 few drops of a 2 per cent potassium iodate solution, and 2 or 3 crystals of 

 potassium iodid. 



The author found it a disadvantage to operate with the wide distillation 

 tube and preferred to titrate the unused standard acid (hydrochloric or sul- 

 phuric) with a centinormal sodium hydroxid solution, using cochineal as the in- 

 dicator. The quartz tube may be replaced by a hard glass tube. 



Nephelometry in the study of nucleases, P. A. Kober and Sara S. Graves 

 {Jour. Amer. Chem. Soc.. 36 {1914), No. 6, pp. 1304-1310, figs. 2).— A description 



" Biochem. Ztschr., 49 (1913), No. 1-2, pp. 19-39, flgs. 4 ; 51 (1913), No. 3, pp. 193-199, 

 fig. 1. 



