SUPERPHOSPHATE OF LIME. 171 



therefore, very desirable tliat sufficient water sliould be used 

 to produce this g-reat heat, which facihtates the dissolving- 

 process ; and the quantity above stated, or, if more conve- 

 nient, the same measure of water as of acid, which Vvill be 

 rather more than half the v.eight, will be a very good pro- 

 portion. More should not be used, as no usefid purpose will 

 be accomplished. In an experiment tried last year with 

 different proportions of water, I could not detect any differ- 

 ence in the result. The water should be appKed first by 

 means of a watering-pot, so that it may be intimately 

 combined with every portion of the bones. This is an 

 important point, and greatly facilitates the dissolving pro- 

 cess, which without it is very likely to be imperfectly 

 accomplished. 



Another reason for applying the water first is, that the 

 bones becoming partially saturated, the acid, from its great 

 affinity for it, rushes as it were into the pores of the bones in 

 seorch of the v.ater, and thus the bones become more rapidly 

 and perfectly mixed with, and acted on by the acid. When 

 no water is employed, and the bones are not entirely in the 

 state of fine dust, as they never are, unless pxu'posely sifted, 

 the surfaces of the small pieces of bone become acted on by 

 the acid, and a coat forms around them which seals up the 

 interstices of the bones, and jjrevents the acid from penetrat- 

 ing. I have no doubt this is often the case likewise from 

 careless or imperfect mixture, and the good effects of the 

 manure are thus materially diminished. 



4. Mode of mixing the bones with the acid, and of prepar- 

 ing the compost. 



It has been recommended that a large heap of ashes or 

 moidd should be made with a hole or depression on the top, 

 in which the bones are to be placed, the acid poured over 

 them, and after some time the whole shovelled up and mixed 

 together. Now, if we examine into the effects of this mode 

 of procediu'e, we shall readily perceive the objection to which 

 it is subject. The ashes, no doubt, contain a considerable 

 portion of carbonate of lime besides other salts, for which 

 sulphuric acid has a very strong affinity. Thus the bones 

 are robbed of a large proportion of the acid, of which they 

 ought to have exclusive possession. And even if common 

 mould is used, or any other substance which has no particular 

 chemical affinity for the acid, still this mould will mechaui- 

 cally absorb much of the acid, and thus deprive the bones of 



