172 MANURES. VII. 



Calcium thiosulphate. 



CaSO t -fO=CaSO 4 . 



The composition of fresh gas lime (from London gas works) 

 is, according to Guyard* 



Calcium hydrate ... ... 15-10 



,, carbonate ... ... 24-20 



,, thiosulphate ... 11-80 



sulphide ... ... 6-90 



,, oxy sulphide... ... 3 -20 



,, sulphate ... ... 0-25 



,, sulphite ... ... 1-50 



,, cyanide ... ... 0*25 



Iron sulphide ... ... 0'55 



Sulphur ... ... ... 4-30 



Silica ... ... ... 1-80 



Alumina ... ... ... 0-70 



Magnesia ... ... ... trace 



Tar ... ... ... 0-25 



Water 29-20 



100-00 



If the unoxidised sulphur compounds remain in gas lime 

 until its application to the land, great harm and sometimes 

 total destruction of vegetation may ensue. In view, then, of 

 the uncertainty of its action its general use cannot he recom- 

 mended. 



Copper Sulphate. Though this substance cannot act as a 

 direct plant food and has seldom (or perhaps never) been used 

 as a manure, some results obtained when spraying crops for 

 disease or for the purpose of destroying charlock, &c., seem to 

 indicate that it acts as a powerful stimulus to the growth of 

 certain plants, for in many cases distinctly beneficial effects 

 have been observed from its use in the case of grain crops and 

 potatoes, where no charlock or disease was present. 



* Bull. Soc. Chim. xxv. 103 ; Jour. Chem. Soc. 1876, ii. 123. 



