SOIL, PHYSICS, CHEMISTRY AND MICROBIOLOGY 945 



tion of Azotohader in cultures (selected cultures) ; methods emplo\'ed to isolate 

 it ; its growth in different solid and liquid nutritive media ; influence of 

 temperature, aeration, etc. He devotes his chief attention to the problem 

 of the fixation of free atmospheric nitrogen, and in particular the conditions 

 ensuring the highest efficiency of the species under study, with reference not 

 only to the absolute quantity of nitrogen fixed, but also to the quantity of 

 non-nitrogenous substances oxydised. 



732 - Method for the Estimation of Hygroscopic Moisture in Soils. — haigh w. d. (Sd 



Proc. R03-. Dublin Soc, XIV, 52')-534, i<)if,). Journal oj the Societv of Chemical Industry, 

 Vol. XXXV, No. ), p. 266, Ivomlon, Feb. 29, 1916. 



The ordinary method of determining the hygroscopic moisture [i. c, the 

 water left after air-drying) in a soil by heating it at about 100° C. for 12-24 

 hours, gives high results owing to the loss of volatile matter other than 

 water. The method now proposed, which gives lower but strictly consistent 

 results, consist.5 in shaking the soil with powdered calcium carbide and mea- 

 suring the acetylene evolved in a nitrometer. The mixing vessel is a thick 

 glass tube shaped like a Kjeldahl flask but with a bent neck; a small test 

 tube fits into the neck but cannot pass the bend. The carbide (about 3 times 

 the weight of soil) is first placed in the bulb : the small tube with the soil is 

 inserted in the upper, bent portion which is kept horizontal ; and then the 

 flexible joint is connected to the nitrometer. The tube is tilted to empty 

 the soil on to the carbide, and the mixture is shaken; the acetylene comes off 

 rapidly and can be measured within a few minutes. A blank experiment 

 should be performed with ignited sar.d and a known weight of water. As 

 found by other workers, the volume of acetylene liberated from 0.018 grms. 

 of water measured 10.5 cc. instead of the theoretical 11.2 cc. The combined 

 water contained in the hydrated sihcates of a soil is practicalh* unaffect- 

 ed by the carbide. 



733 - The Reaction of Soil and Measurements of Hydrogen-Ion Concentration. — 



GiLLESPrE L, J. C. (J. Washington Acad. Sc, VI, 7-16, 1916). Journal of the Society 0' 

 Chemical Industry, Vol. XXXV, No. 4, p. 266. London, Feb. 29, 1916 



The reaction of a soil should be studied from the standpoints of quantity 

 of acid substance, and of intensity of the acidity-. The amount cf Hme. 

 or other neutralising materials required to correct acidity, depends 

 upon the first, but probably the characteristic effects of acidity upon 

 fertiHty are more clearly correlated with the latter, which can only be 

 measured by determining the hydrogen-ion concentration. Twenty-two 

 soils of seven distinct types were investigated from this point of view, 

 both by the electrometric and colorimetric methods. In both of these 

 the soil was air-dried, passed through a coarse sieve, and then mixed with 

 twice its weight of water. The electrolytic vessel, which was shaken conti- 

 nuously throughout the determination, contained a platinum electrode 

 coated with palladium, as a means for filhng the space above the sus- 

 pended soil with pure hydrogen, and at its base a stop-cock to connect 

 the liquid with a saturated solution of potassium chloride. The difference 

 of potential between the platinum and a saturated potassium chloride 

 calomel electrcde was found bv means cf a verv sensitive voltmeter. 



