1919] AGRICULTURAL, CHEMISTRY AGROTECHNY. 13 



by Benedict (E. S. R., 39, p. 112) for the determination of blood sugar. It is 

 pointed out that this precaution must be taken in estimating the monosac- 

 eharids formed by acid hydrolysis of the more complex carbohydrates. 



A system of blood analysis, O. Folin and H. Wu {Jour. Biol. Chem., S8 

 (1919), No. 1, pp. 81-110 figs. 2). — A system of blood analysis, the starting 

 point for which is a protein-free blood filtrate, is described in detail. The de- 

 terminations, which include nonprotein nitrogen, urea, creatinin, creatin, uric 

 acid, and sugar, are all conducted on the filtrate from 10 cc. of the blood. 



The precipitation of the blood proteins is brought about by a new protein 

 pz'ecipitant, tungstic acid, in the following manner: A measured amount of 

 blood is transferred into a flask having a capacity of 15 to 20 times that of the 

 volume taken and diluted with seven volumes of water. To this are added, 

 by means of pipettes, one volume of 10 per cent sodium tungstate (Na2W022H20) 

 and one volume of 2N/3 HaSO*. On shaking, the precipitation is complete 

 within a few seconds. The precipitate can be removed by filtering or, if heated 

 on a water bath for two or three minutes, by centrifuging. Filtration is recom- 

 mended as safer for ordinary work. This precipitation process is said to work 

 equally well with any kind of blood, and is considered by the authors to be 

 superior to all former methods. 



The nonprotein nitrogen determination is made with 5 cc. of the protein-free 

 fUtrate by the nesslerization process of Folin and Denis (E. S. R., 36, p. 316), 

 with certain modifications in method of procedure and preparation of reagents. 



In the urea determination direct nesslei'ization has been abandoned. For the 

 hydrolysis of the urea, use has been made of jack bean urease or the autoclave, 

 and for the isolation of ammonia, aeration or distillation. Any of the four com- 

 binations is said to give satisfactory results, using 5 cc. of the protein-free blood 

 filtrate. The autoclave process is recommended chiefly when a large series of 

 determinations is to be made, or when creatin is to be determined also, as the 

 hydrolysis of the urea can then be accomplished simultaneously with the con- 

 version of creatin into creatinin. 



Folin's colorimetric method is employed for the determination of creatin and 

 creatinin, using 10 cc. of the blood filtrate for preformed creatinin and 5 cc. 

 for creatinin and creatin. One standard creatinin solution suitable both for 

 creatinin and creatin determinations is made by transferring to a liter flask 

 6 cc. of the standard creatinin solution used for urine analysis, adding 10 cc. 

 of normal hydrochloric acid, and making up to the mark with di.stilled water. 



For determining uric acid a modification of the Folin-Denis-Beuedict method 

 has been developed which requires only 20 cc. of the blood filtrate (equivalent 

 to 2 cc. of blood), and which is considered to be more dependable as well as 

 more simple and convenient than the original method. The technique of the 

 process is described in full, including the preparation of a new standard uric 

 acid solution, the keeping quality of which is considered superior to any other 

 as yet devised. The solvent is 10 per cent sodium sulphite, which tends to 

 keep the solution free from dissolved oxygen. 



Sugar is determined In 2 cc. of the blood filtrate by a new colorimetric method, 

 Involving the application of the phenol reagent of Folin and Denis to cuprous 

 oxid obtained by the action of a weakly alkaline copper tartrate solution on 

 the blood sugar. The color produced is said to be intense and stable. 



Note on the determination of urea in urine by direct nesslerization, O, 

 FoLiN and G. E. Youngbueg {Jour. Biol. Chem., 38 {1919), No. 1, pp. Ill, 112). — 

 The authors state that, by using a urease preparation sufficiently free from 

 nitrogenous materials, the urea nitrogen can be nesslerized without any char- 

 coal treatment. The urease solution is prepared by washing 3 gm. of permutit 



