1919] AGRICULTURAL CHEMISTRY AGROTECHNY. 413 



the ratio of reducing sugar to tliiosulphate not varying as in the Clark modifica- 

 tion. 



The principal change is the use of dilute acetic acid to acidify the solution 

 after the precipitation of the cuprous oxid. As this has no effect upon cuprous 

 oxid, a known excess of iodin may be added and the cuprous oxid then dissolved 

 by the addition of a very small quantity of hydrochloric acid. The cuprous 

 chlorid formed is immediately acted upon by the iodin, and consequently no 

 precautions against oxidation by the air are necessary. As soon as the cuprous 

 oxid has been entirely dissolved by the hydrochloric acid the excess of iodin is 

 titrated with thiosulphate, using starch as an indicator. 



The method may be used for any reducing sugars. 



A note on the determination of the inorganic constituents of blood and 

 other physiological material, I. Greenwald (Jour. Biol. Chem., 38 {1919), No. 

 3, pp. It39, 440 ) . — The author calls attention to the method previously described 

 incidentally (E. S. R., 35, p. 714) of separating the organic constituents of the 

 blood from the inorganic by precipitation with picric acid. With blood it is con- 

 sidered advisable to dilute to almost 10 volumes with water, add 1 per cent of 

 acetic, hydrochloric, or sulphuric acid, saturate with picric acid, and then dilute 

 to an exact multiple. After standing a few minutes the mixture can be filtered 

 and measured portions of the protein-free filtrate taken for the analyses. 



A table is given of the values obtained by the author with this method for 

 the sodium, potassium, calcium, and " acid-soluble " phosphorus of dog blood 

 and serum. 



Determination of ammonia in the blood, S. Morgulis and H. M. Jahr {Jour. 

 Biol. Chem., 38 {1919), No. 3, pp. 435-438).— The essential features of the method 

 described consist in precipitating the blood proteins with m-phosphoric acid as 

 soon as the blood is taken (to prevent the splitting off of ammonia), adding a 

 known amount of standard ammonium sulphate to the blood filtrate to increase 

 the ammonia content sufficiently to make it possible to examine the color pro- 

 duced by the nesslerization without changing the colorimeter, and absorbing 

 the ammonia by permutit, which does away with the necessity of driving off the 

 ammonia by aeration. The conti'ol is made with Ringer's solution, to which 

 the same reagents are added in equivalent amounts. The technique of the 

 method is described in detail, and a series of determinations of ammonia in the 

 blood of normal individuals is given. 



Note on the Levds-Benedict method of blood sugar determination, S. Mor- 

 gulis and H. M. Jahe {Jour. Biol. Chem., 39 {1919), No. 1, pp. 119-123) .—DaXa. 

 are presented whch show that the presence of creatiuin increases the blood 

 sugar value as determined by the Lewis-Benedict method. Concentrations of 

 less than 2 mg. of creatinin per 100 cc. were found to have no effect upon the 

 accuracy of the reaction, but with greater concentration the error in the sugar 

 analysis increased progressively. The method is therefore considered by the 

 authors to be without value' in the sugar analysis of blood containing more than 

 3 mg. of creatinin per cubic centimeter. 



A method for determination of minute amounts of lead in urine, feces, 

 and tissues, W. Denis and A. S. Minot {Jour. Biol. Chem., 38 {1919), No. 3, pp. 

 449-452). — The process, which is described in detail, " consists essentially in the 

 removal of most of the organic matter by fusion with sodium nitrate, the pre- 

 cipitation of tlie lead as sulphid, its electrolytic deposition as lead peroxid, and 

 the titration of the iodin liberated from potassium iodid when the lead peroxid 

 deposit is treated with dilute acid." 



The authors have been able to recover by this method lead added to urine, 

 feces, and tissues in amounts varying from 0.5 to 4 mg. to the average extent of 

 95 per cent of the amount added. 



