328 COMMON SALT. 



quantity of carbonate of potash : in fact, the potash 

 of commerce, the chief source of the alkali, is the ash 

 of trees; whilst kelp, the ash of sea-plants, consists 

 chiefly of carbonate of soda. Both pot-ashes and kelp 

 are good manures in moderate quantity, but their 

 -value depends as much on the earthy phosphates 

 which they contain as on their alkaline salts. 



891. Muriate of potash or chloride of potassium 

 is sometimes used as a dressing for grass-land. The 

 petre salt of the nitre-refiners contains a large quan- 

 tity of this salt. It used formerly to be obtained in 

 large quantities by the soap-boilers, who mixed salt 

 with their potash soap; the salt was decomposed and 

 a hard soda soap and chloride of potassium in solu- 

 tion were the results. The soap-maker's spent lees 

 were considered a valuable manure for grass-land, 

 and were believed to destroy moss (524). 



892. Chloride of sodium or muriate of soda 

 (common salt), is frequently recommended as a valu- 

 able manure ; and in many soils, particularly those 

 containing little chlorine, it produces very marked 

 effects, when applied in moderation. It is by many 

 stated that cattle thrive better on plants which have 

 been manured with a small quantity of common salt, 

 than on those not so manured. Common salt is not 

 unfrequently added to dung with a view of facilitating 

 its putrefaction ; it is very improbable that any such 

 effect should be produced by salt, which in fact is 

 more likely to retard decomposition. 



893. Common salt is sometimes recommended to 



