714 EXPERIMENT STATION EECORD. [Vol.43 



vacuum method if sufficient time is allowed. If tliese methods are accepted as 

 standards, then the Hopkins method seems to give correct results when used to 

 measure the reduction in soil acidity by applications of lime. It may also 

 measui-e with accuracy the most immediate lime need, although it does not 

 measure the total power of a soil to decompose carbonates. 



" If we assume that the reduction in acidity s'hould be approximately the same 

 for all limed plats, the Hopkins method and the hydrogen electrode show the 

 highest percentage consistency." 



Determination of nitrate nitrogen in nitrates and fertilizers, H. C. Moore 

 (Jour. Indus, and Engin. Chem., 12 (1920), No. 7, pp. 669-673).— The author 

 outlines briefly the methods commonly employed for the determination of 

 nitrate nitrogen in nitrates and fertilizers, and describes a modified Kjeldahl- 

 Gunning method which, if correctly applied, is said to yield extremely accurate 

 results. The method is based upon the following reactions : 



OH OH 



(1) 2 C«U,<^ +2 NaN03+H2SO.=2 C6H4<" +2 C02+Na2SO«+2 H.O 



COOH NO2 



(Salicylic acid) (Nitrophenol) 



OH OH 



(2) C6H4< +3 H.=C6H4^ +2 H,0 



NO2 NHo 



(Aminophenol) 



OH 



(3) 2 C6H^<^ +27 H..S04-=(NH4)2S04+12 CO.+20 SO,+.'? H^O 



.NH. 



The reduction of the nitrophenol may be brought about either with the use 

 of " hypo " or zinc dust, although the author prefers the former. The technique 

 of tlie method as applied to nitrates is as follows : 



Fifty cc. of salicyl-sulphonic acid, prepared by making up 40 gm. of salicylic 

 acid to one liter with concentrated H2SO4, is slowly added to 0.8517 gm. of 

 NaNOa in a Pyrex Kjeldahl flask, and the flask warmed over low heat or in boil- 

 ing water or steam bath, shaking frequently until the solution is- complete. 

 Five gm. of " hypo " is added and the heating continued until frothing ceases 

 (about 5 minutes), after which 10 gm. of sodium or potassium sulphate and 1 

 gm. of mercury are added, and the digestion continued with rapid boiling for 

 one hour after the solution has become clear. The solution is then diluted with 

 water to about 400 cc, a small piece of granulated zinc and from 70 to 80 cc. of 

 caustic soda (made by dissolving 30 lbs. of commercial soda in 2.5 gal. of water) 

 containing 2 gm. of fused sodium sulphid are added, and the ammonia is dis- 

 tilled into 21 cc. of N/2H2SO4 diluted to 125 or 150 cc. with water containing 3 

 drops of alizarin sulphonate. The distillation is continued for about 45 min- 

 utes, or until about 150 or 200 cc. of the distillate Is collected. Blanks should be 

 run with all reagents and the correction thus obtained applied. 



Essentially the same technique is employed in the case of fertilizers, using 

 1.7034 gm. of the sample, 35 cc. of salicyl-sulphonic acid, 5 gnij of " hypo," 5 

 gm. of potassium or sodium sulphate, 0.5 gm. of mercury, and 1 gm. of sodium 

 sulphid. 



The results are summarized of a large number of determinations on nitrate 

 samples and mixed fertilizers and of a comparison of this method with the 

 West Coast or refraction method. 



The Hess-Ives tint-photometer and its use with raw sugars, G. P. Meade 

 and J. B. Haeeis (Jour. Indus, and Enf/in. Chem.. 12 {1920), No. 7, pp. 686- 

 688, fig. 1). — The authors discuss the Hess-Ives tint-photometer and the diffi- 



