Phosphatic Materials used for Agricultural Purposes. 21 



The first analysis, more especially, has evidently been done in 

 a very careless manner, for bone-ash prepared from pure bones 

 does not contain so high a percentage of phosphate of lime as 

 this sample of the commercial article is reported to contain. 

 The proportion of charcoal, moisture, and sand three matters 

 not properly belonging to pure bone-ash, amount to 10 per cent, 

 in round numbers. Deducting these accidental constituents, and 

 calculating the results for pure bone-ash, the latter would contain 

 no less than 97*66 per cent, of bone-earth. It is hardly con- 

 ceivable how such absurd results as those contained in the first 

 analysis can be committed to paper by an analytical chemist. 



If these were solitary instances I would take no further notice 

 of analyses the incorrectness of which is proved by abundant 

 internal evidence. But unfortunately this is not the case. 

 Bone-ash is usually sold by importers at a price depending upon 

 the percentage of phosphate of lime in it, and hence it is not 

 the interest of dealers to have the determination of bone-earth 

 made by a chemist who states the amount correctly, but rather 

 to employ an analyst who, adopting an expeditious and incorrect 

 method, makes the percentage of phosphates 3, 4, and even 6 

 per cent, higher than it is in reality. The importance of this 

 subject has led me to examine minutely the composition of pure 

 and of commercial bone-ash. i 



The mineral portion of pure bones or pure bone-ash has 

 been repeatedly examined by various chemists. The more 

 recent researches by Professor Heintz, of Berlin, deserve espe- 

 cial notice. According to Heintz, the phosphate of lime present 

 in bone-ash is a combination of 3 equivalents of lime and 1 

 equivalent of phosphoric acid ; its formula consequently is 

 3 C O + P O 5 . Although some chemists still retain the older 

 formula 8CO+3PO 5 assigned to bone-earth by Berzelius, 

 most agree with Heintz in considering the chief constituent of 

 bone-ash to be the tribasic phosphate of lime. In the analyses of 

 human and other bones, the same gentleman obtained a certain 

 proportion of lime, which was neither united with phosphoric 

 acid, as tribasic phosphate, nor with carbonic acid. This excess 

 of lime is calculated in Heintz's analyses as fluoride of calcium. 

 Thus he states in one place that human bones contain 3*52 per 

 cent, of fluoride of calcium ; in another analysis he gives 3'82 

 per cent, of fluoride of calcium in bones dried at 212 Fahr. It 

 should be mentioned, however, that no direct fluorine determina- 

 tion has been attempted, but that the result has been obtained 

 by calculation. Every chemist is acquainted with the fact that 

 bones contain small quantities of fluorine ; but, at the same time,, 

 considerable difficulty is experienced occasionally in obtaining 

 with recent bones a deep etching upon glass, even if large 



