MANURES AND FERTILIZERS. 137 



The table of manurial analyses in Appendix shows 

 how deficient ordinary stable manure is in potash, and 

 how few substances furnish it in liberal proportion. 

 Thus the deficiency of potash, both in the soil and in 

 ordinary manurial substances, must be made good. But 

 while potash is of paramount importance to the tobacco 

 plant, great care must be exercised to exclude all con- 

 tamination with chlorine. Potash combines freely with 

 chlorine, and in the muriate of potash is wholly present ; 

 common salt (chloride of soda) is also frequently found 

 in many potash salts. But the demand for a potash salt 

 free from this defect has caused the introduction of high 

 grade sulphates that are practically free from chlorine. 



Potash Salts are obtained from the potash mines at 

 Stassfurt, Germany, and are largely used for manurial 

 purposes, both in Europe and this country. The native 

 salt is a mixture of sulphate and muriate of potash with 

 common salt, and is clarified after mining. Kainit, the 

 lowest grade sulphate, contains 25 per cent of sulphate 

 of potash (equal to 12 per cent actual potash), and 60 

 per cent of common salt, and should never be used for 

 tobacco because of this last defect. Muriate of potash, 

 80 per cent purity, contains 50 per cent actual potash, 

 and about 15 per cent common salt, and for this last 

 reason is eschewed by tobacco growers. The first salt 

 satisfactory for tobacco culture was the double sulphate 

 of potash and magnesia, or double-manure-salt, and it 

 is still used with good results. As its name implies, 

 toe sulphuric acid is combined with potash and mag- 

 nesia, and also with soda to some extent ; its analysis 

 is given in Table IV, Page 112. But it contains so 

 much chlorine that it is not now approved for fine 

 wrappers, and the Poquonock results are against it. 

 Whether its magnesia is of much use is also a question. 

 Double manure salt is usually sold on a guarantee of 

 48 to 50 per cent sulphate of potash (equal to about 25 



