SOILS AND MANURES. 359 



into a wine-glass, and upon this a teaspoonful of slaked 

 lime, and, adding a few teaspoonfuls of water, shake the 

 mixture briskly. The stronger the smell of ammonia the 

 better is the guano, for the lime, by taking away the acids 

 that are united with the ammonia, sets that pungent sub- 

 stance free. 3. Vinegar Test. If on pouring vinegar upon 

 guano a strong effervescence ensues, we infer that there 

 has been an intentional adulteration with carbonate of 

 lime. 4. Test with Hot Water. Make a filter of blot- 

 ting-paper, folded together in the form of a cone, and put 

 it into a common funnel. Put into this fifteen grammes 

 of guano well dried, and pour upon it hot water as long as 

 it passes through of a yellow color. Now dry the filter, 

 and, weighing the dried powder which is upon it, you find 

 what proportion of the guano is dissolved, or, in other 

 words, what proportion of ammoniacal salts it contains, for 

 it is this part of the guano alone that is soluble. 



501. Ammoniacal Salts. The salts of ammonium, some 

 of which, as you have seen, are the principal source of the 

 fertilizing power of guano, are chiefly the chloride, or sal 

 ammoniac, the sulphate, the nitrate, the humate (formed 

 with the acid of humus), and the carbonate or salt of harts- 

 horn. These salts are present in stable manure, and in oth- 

 er fertilizing substances which furnish nitrogen to plants. 

 There is considerable ammonia in the gas-liquor which is 

 formed in the process of cooling and purifying the gas. 

 This liquor is very valuable for manure. There also is con- 

 siderable ammonia in soot, and hence this substance is a 

 good fertilizer. 



502. Bone-Dust. The powder of bones is an exceedingly 

 valuable manure, as you can readily see it would be from 

 observing the composition of bone. A bone is composed 

 of an animal part, gelatin, and a mineral part, nine tenths 

 of which is phosphate of lime, and one tenth the carbonate. 



