SOILS FERTILIZERS. 623 



Saltpeter, T. H. Holland and L. L. Fermok (Rec. Geol. Survey India, 39 

 (1910), pp. 196-20!^) .—TM^ article explains ttie conditions essential to the 

 formation of saltpeter, describes the methods of manufacture followed in India, 

 and gives statistics of distribution and export. 



The nitrate is prepared by leaching the soil around villages and separating 

 the sodium chlorid and potassium nitrate by fractional crystallization. 



The average annual export during the 5 years 1903^ to 1907-8 was about 

 20,103.38 tons valued at $1,285,904.75, the United States being one of the largest 

 consumers. Calcutta is the chief port of shipment, handling over 98 per cent 

 of the total product. 



Saltpeter, T. H. D, La Touche {Rec. Geol. Survey India, 40 (1910), pt. 2, 

 p. l-'fO). — Statistics of export and distribution during 1908 and 1909 of saltpeter 

 produced in India are given. It is shown that of the 22,076.98 tons of this 

 material produced in 1909, 7,469.39 tons was sent to China, 4,709.38 to the 

 United States, and 4,564.17 tons to the United Kingdom. 



A contribution to the study of calcium cyanamid, C. Brioux (Ann. Set. 

 Agron., 3. ser., 5 (1010), I, No. J,, pp. gZ/i-^Si ) .—This is a full account of inves- 

 tigations briefly reported elsewhere (E. S. R., 24, p. 323). 



The author found that only about one-half the weight of commercial calcium 

 cyanamid consists of the pure compound, the other half being made up of free 

 lime, carbon, and other impurities. It contains only traces of dicyandiamid and 

 other complex and undetermined compounds. The commercial product under- 

 goes marked changes under the influence of the moisture and carbon dioxid of 

 the air, as is shown by a moistening of the mass,* and finally a perceptible loss 

 of ammonia. 



As prepared by the moi-e improved methods the loss of nitrogen on storage is 

 relatively small. When stored in thin layers in a dry place a loss of from 1.7 

 to 1.8 per cent of the total nitrogen in the course of 8 months was observed. 

 When stored under moist conditions, however, the loss was 8 per cent in the 

 same time. Left in bags over two winters and a summer in a moist climate the 

 loss of nitrogen in the form of ammonia was 13.5 per cent. When applied to the 

 soil in normal amounts there is no loss of ammonia, the ammonia formed being 

 absorbed by the soil and nitrified. 



Methods of studying the chemical composition of the cyanamid and its trans- 

 formation products are described. It is shown by means of these that under 

 the iufiuence of moisture and carbon dioxid the lime of the cyanamid is hydrated 

 and carbonated, and more or less of the cyanamid is set free, polymerizing into 

 the form of dicyandiamid, with the accessory production of small quantities of 

 complex nitrogenous compounds. 



It was found that calcium cyanamid stored in a dry place for 8 months con- 

 tained from 10 to 15 per cent of its total nitrogen in the form of dicyandiamid, 

 while that stored under moist conditions contained 80 per cent or more of its 

 total nitrogen in that form. 



The results of pot experiments made by the author confirmed the conclusion 

 of Immendorff and Kempslii (E. S. R., 20, p. 220) as to the toxicity of the 

 dicyandiamid, but did not sustain that of Ulpiani (E. S. R., 24, p. 226) that 

 the transformation of calcium cyanamid is primarily a purely physico-chemical 

 process. When applied to the soil in normal amounts this compound produced 

 characteristic injuries to plants, particularly buckwheat, as shown in the curl- 

 ing and drying of the extremities of the leaves. The result was the same 

 whether the dicyandiamid was used in the pure state or in the form of altered 

 calcium cyanamid. the extent of injury depending upon the amount of diacyan- 

 diamid applied. In all cases the cyanamid which had undergone alteration pro- 

 93315°— No. 7—11 3 



