282 APPENDICES 



or pulverized, the more surface it exposes to the action of 

 water, and the more rapidly it dissolves. By grinding, it is 

 only possible to reduce the bones to a gritty dust, fine perhaps 

 to the eye, but still coarse when seen under the microscope. 

 Chemistry furnishes a cheap means of extending the sub- 

 division to a very great degree. 



And this brings us to the superphosphate. This compound 

 consists, in 100 parts, of Phosphoric acid, 71^ ; Lime, 28y 2 . 



As prepared for agricultural purposes, it is largely mixed 

 with other substances, as the analyses show. Unlike the phos- 

 phate, it dissolves easily in water. It differs in composition, 

 from the phosphate, only in the proportion of its ingredients. 

 If we add a certain amount of phosphoric acid to the phos- 

 phate, we shall obtain the superphosphate. It may also be 

 procured by taking away lime from the phosphate. In prac- 

 tice, we do the latter. If we add to bones, one-third their 

 weight of sulphuric acid (oil of vitriol), a portion of lime 

 quits the phosphoric acid and unites with sulphuric acid, 

 forming sulphate of lime (gypsum) ; while the phosphoric 

 acid, thus set free, combines with the undecomposed phos- 

 phate, forming superphosphate. 



Let the reader add a tea-spoonful of superphosphate to a 

 tumbler half full of water, and after a little stirring, allow it 

 to settle, and pour off the clear liquid into another tumbler. 

 (If no superphosphate is at hand, use instead of the liquid 

 just mentioned, strong vinegar in which some pieces of bone 

 have stood for a few days.) Then prepare a solution of 

 saleratus, or soda, in water, and pour it gradually into the 

 first liquid. Presently a white cloud, or precipitate, as chem- 

 ists call it, will be formed; at the same time the liquid will 

 foam like soda-water, from the escape of carbonic acid gas. 



This white cloud is precipitated phosphate of lime, and is 

 the same as bone-earth phosphate except that it is inconceiv- 

 ably finer than can be obtained by any mechanical means. 

 The particles of bone-dust will not certainly average smaller 

 than 1-1000 of an inch, while those of this precipitated phos- 



