Potassic Manures 



Another source of supply is the salt marshes 

 of the French Midi, which contain nearly 45 per 

 cent. K20- These muriates can be distinguished 

 because they contain sulphate of magnesia (MgS04) . 



When buying, a guarantee of the title of the 

 manure is essential, and that with the highest title 

 must be bought. It is a suitable potassic manure 

 for almost every kind of crop, but should not 

 be used on tobacco, because of its chlorures, while it 

 gives a poor flavour to potatoes. 



Sulphate of Potash or Potassium Sulphate 

 (KoSOJ. 



This is in the form of a white salt crystallised in 

 prisms, and thus is distinguished from KCl, which 

 crystallises in cubes. The crystals resist the action 

 of the air ; they have a salt taste with a bitterness 

 which also distinguishes them from KCl, and more- 

 over they are relatively less soluble in water. 



The manure is made by making sulphuric acid 

 (H2SO4) react on chlorure of potash (KCl) or on 

 carbonate of potash (K2CO3). The chief source of 

 supply of sulphate of potash is still the beds 

 of Stassfurt. It is obtained by the treatment of 

 carnallite, and contains nearly 50 per cent. 

 K2O. 



In France it is made from the salins of beet- 

 root and then contains nearly 50 per cent, potash. 



It has also been made in Scotland from seaweed 

 ash. 



This sulphate is the potassic manure for tobacco, 

 because it contains no chlorure, which is injurious 

 to the quality of that crop. 



73 



