KELP AND ALUNITE 



237 



per cent., or ignited and the leached potassium sulphate 

 evaporated, when the nearly pure potash salt can he obtained. 



Fig. 55. — Giant kelp. 



The latter process, however, is expensive. Both kelp and 

 alunite have given good results as a fertilizer with no treat- 

 ment other than drying in the case of kelp and pulverizing 



