298 IMPROVEMENT OF THE SOIL 



soaps, which, as salts, produce a most powerful effect in the 

 processes of vegetation. 



1. Soap-boilers^ spent lye. In the process of soap-making, 

 the alkali combines with the acid of stearine, margarine and 

 oleine, forming stearates, margarates and oleates or soaps, 

 while the glycerine remains in solution with the salts. 



This latter substance is somewhat similar to geine, and is 



thus constituted. 



Carbon 40.07 I Hydrogen 8.92 



Oxygen 51.00 



The oxygen, hydrogen and carbon exist in such proportions 

 as to form water, carbon and carbureted hydrogen. It may 

 yield to plants the same elements as humic acid. As about 

 8 per cent, of oils and fats is glycerine, it will readily be per- 

 ceived, that the large quantity of this substance in spent lye, 

 must render it a very valuable manure. 



But this is not the only substance which gives to it its 

 value. There are also various salts ; the kind depending 

 upon the alkali used to form the soap. 



1. If potash is used (as it always is to form soft soaps), 



every 100 lbs. of soft soap requires about 8 bushels of ashes, 



and the spent lye contains, of 



Sulphate of potash 6.5 lbs. I Silicate of potash 1.8 lbs. 



Muriate of potash 0.3 " | 



and a small quantity of potash in a free state. This adds 

 greatly to the value of this article as a manure. 



2. If now common salt is added to make the soap grain, or 

 to convert the soft to hard soap, the salt is decomposed, the 

 soda takes the place of the potash, and forms soda soap, while 

 thechlorine combines with the potassium, forming the chlo- 

 ride of potassium (muriate of potash), which is added to the 

 spent lye. The quantity will depend upon the quantity of 

 salt* used. 



* In a boil of 2,000 lbs. of soap, about 7 bushels of salt are usually 

 added. 



