SULPHATE OF LIME. 65 



SULPHATE OF LIME. 



Sulphate of Lime, or Gypsum, is extensively 

 applied to the soil as a manure; every 100 

 Ibs. contain 46.51 Ibs. of sulphuric acid, 32.56 

 Sbs. of lime, and 20.93 Ibs. of chemically com- 

 bined water. The value of gypsum as a 

 manure has been erroneously attributed to its 

 absorbent properties in attracting and retaining 

 moisture. Extended experiments have proved 

 that it is almost destitute of any absorbing 

 power; 100 parts of gypsum will absorb only 1 

 part of water in 12 hours, while loamy clay ab- 

 sorbs 25 parts, and ordinary soil 16 parts. These 

 experiments were extended to 72 hours, but the 

 gypsum absorbed no moisture after the first 12, 

 which demonstrated that 1 part to 100 is the 

 limit of its absorbent power ; while loamy clay 

 and ordinary soil absorbed in that time 35 and 

 23 parts, respectively. Professor Schuebler per- 

 tinently remarks, when speaking of this fact : 

 " Thus theories which are written down, often 

 fall to nothing when tested by experiment." 



The beneficial action of gypsum must be traced 

 to some other cause. As it is composed of lime 

 and sulphuric acid, the benefits resulting from 

 its application must be due to one or both of 

 these substances. Recent experiments of distin- 

 guished chemists, seem to prove that the action 



