No. 4.] CHEMICAL AND FARM MANURES. 135 



Two other sources of potash should be mentioned in this 

 category, namely, the nitrate of potash and the carbonate of 

 potash and magnesia. The former, known as saltpetre and 

 employed in the manufacture of gunpowder, contains about 

 14 per cent of nitrogen and 44 per cent of potash. Its cost 

 is usually so great as to preclude its general use for agri- 

 cultural purposes. The carbonate of potash and magnesia, 

 containing about 21 per cent of potash and 19 per cent of 

 magnesia, may be used as a substitute for muriate of potash 

 wherever plants are grown whose quality is susceptible to 

 injury by the chlorine of the muriate. It has not jQi been 

 generally introduced into this country, and has commanded 

 too high a price to bring about its extensive employment. 

 All of these sources of potash may be safely drawn upon 

 for the growing of hops, sugar beets, a fine quality of pota- 

 toes, and other plants which may be injured by the use of 

 muriate of potash or kainite ; but for tobacco nitrate of 

 potash would be objectionable. 



High-grade sulfate of potash, containing about 48 per 

 cent of potash, has been quite generally recommended in 

 Europe and the United States for growing the crops just 

 enumerated, since it is practically free from chlorine, 

 though for tobacco it has not given as good results in the 

 experiments conducted by the Connecticut station at New 

 Haven, as certain of the sources of potash already discussed. 

 Where potatoes are grown for the production of starch, the 

 high-grade sulfate of potash is usually employed, since, un- 

 less applied the previous season, the chlorine contained in 

 kainite and muriate of potash depresses the starch content. 

 In the potato-growing sections of Rhode Island the farmers 

 generally consider that a mixture of about equal parts of 

 high-grade sulfate and of muriate of potash gives upon an 

 average better yields than either one alone ; and experiments 

 at the Rhode Island station this season indicated that, so far 

 as concerns yield, a mixture of the two or the muriate alone 

 was slightly superior to the sulfate alone. Probably in a 

 dry season the muriate of potash would have the advantage 

 over the sulfate by virtue of its greater solubility. 



For orchards, meadows and most garden crops the tnuri- 

 ate of potash , containing about 50 per cent of actual potash 

 or 80 to 85 per cent of muriate of potash, is considered the 



