Miscellaneous Fertilizing Materials 117 



tities, particularly for clover, and it is believed that its 

 favorable effect was due, not so much to the direct addition 

 of lime, as to its action upon insoluble potash compounds 

 in the soil, in setting free potash. Thus the application 

 of plaster caused an increase in crop, because of the potash 

 made available. 



We have in the eastern states two main sources of gyp- 

 sum, namely, Nova Scotia and Cayuga, New York. Nova 

 Scotia plaster contains on the average over 90 per cent of 

 sulfate of lime, and is, therefore, purer than that obtained 

 from Cayuga, which often shows as low as 65 per cent 

 of pure sulfate ; the latter, however, frequently contains 

 appreciable amounts of phosphoric acid. 



Phosphorus powder. 



In many places it is possible to obtain plaster which is a 

 waste in the manufacture of phosphorus. This waste 

 contains the plaster in a precipitated form, and frequently 

 also contains considerable amounts of phosphoric acid. 

 The disadvantage of this waste lies in the fact that it is 

 frequently wet and lumpy, and thus not easily handled 

 and distributed. Its advantage lies in its content of 

 phosphoric acid, which ranges from 1.5 to 2 per cent, 

 though as a rule, it can be purchased at a lower price a 

 ton than that from the regular sources. 



Calcium carbide waste. 



Calcium carbide waste is a by-product obtained in the 

 manufacture of acetylene gas. It is a solid residue con- 

 sisting chiefly of calcium carbonate, calcium hydrate and 

 water. It is valuable as a source of lime only when it 

 may be secured at an extremely low cost because it is 

 usually wet or otherwise in very poor mechanical condi- 



