136 Analyses of Books. [Feb^ 



Article VII. 



Analyses of Books. 



Memoirs of the Literary and PhUosopkical Society of Manchester y. 

 Second Series. Vol. III. 1819. 



This volume of 512 pages contains 24 papers : 



I. Experiments and Observations on Phosphoric Acid, and^ on 

 the Salts denominated Phosphates. By John Dalton. — This 

 paper was read to the Society in the beginning of 1813, a cir- 

 cumstance which must not be forgotten while taking a view of 

 its contents. Since that time experiments have been made on 

 the subject by Berzehus, Dulong, Davy, and myself. Of every 

 thing brought to hght by these experiments, Mr. Dalton must 

 have been ignorant when his paper was ])rinted, or at least when 

 it was read ; for in a note at the end of his paper (dated Oct.. 

 1817), he notices the labours ofBerzelius, Dulong, and myself; 

 but still adheres to the opinions given in his paper. This being" 

 the case, I think it needless to enter into any controversial dis- 

 cussion. I shall, therefore, just give an account of Mr. Dalton's 

 opinions, and, for my own, refer the reader to my review of the 

 Philosophical Transactions for 1818, and to the chapter in my 

 System of Chemistry, in which I give an account of the 

 phosphates. 



Mr. Dalton conceives that phosphoric acid might be obtained 

 at a much cheaper rate from the earth of bones than by treating 

 phosphorus with nitric acid. There is no doubt of thisv But he 

 has not given any process by which such an extrication can be 

 accomplished. The following would probably answer : Saturate 

 the quadriphosphate of lime, which remains after the earth of 

 bones has been decomposed by sulphuric acid, with ammonia ; 

 filter ; evaporate the solution to dryness ; and expose the dry 

 salt to a red heat. Pure phosphoric acid will remain behind. 

 This process will cost a quantity of sulphuric acid nearly equal 

 to the weight of the earth of bones employed. The quantity of 

 carbonate of ammonia requisite to saturate the acid will be at 

 least equal to double the weight of the earth of bones. 



Mr. Dalton finds the composition of earth of bones as follows : 



Carbonic acid 3 



Lime , . 11 



Phosphate of lime 86 



100 



He thinks that 84- parts of concentrated sulphuric acid will be 

 necessary to decompose 10 parts of earth ot bones. The acid 

 product obtained is either an octophosphate or dodecaphosphate. 



