2/2 AGRICULTURAL ANALYSIS 



(1) Five or six reagents are required. 



(2) Evaporations and ebullitions of alkaline liquids are carried 

 on in glass vessels, which are subject to attack. 



(3) The precipitate weighs only a few centigrams. 



(4) The precipitate is mixed with silica. 



(5) The precipitate is soluble in the successive reagents em- 

 ployed. 



These objections are answered by L,asne. 30 



Lasne admits that if the phosphates in which fluorin is to be 

 determined are previously ignited, many of the objections to the 

 shorter method proposed by Carnot are removed, but he fears 

 that there is danger of loss of fluorin, as well as of water, by 

 calcination, and adds that the calcination of phosphates, and more 

 particularly of bones,- is an operation which is neither easy nor 

 rapid, if it be desired to burn away the last traces of carbon. 



232. Protection of Glassware in Working with Fluorin. Carnot 

 has proposed to coat the surfaces of flasks and tubes used in the 

 determination of fluorin with gum-lac. 31 



According to Carnot, this lacquer protects completely the glass 

 from the action of the solution of hydrofluoric acid. 



233. Fluorin in Bones. According to Carnot, the deposits of 

 phosphates have been formed in the following manner: 



(1) The accumulation of phosphatic animal debris, etc., along 

 the banks of the ocean or in lakes or lagoons. 



(2) The impregnation of these phosphates in the fluorid of cal- 

 cium contained in the sea waters. Carnot has demonstrated the 

 presence and determined the proportion of fluorin in the waters 

 of the ocean, and has shown in the laboratory, by synthetic ex- 

 periments, the gradual fixation of fluorin in bony deposits. 



The fluorin which is a constituent of mineral phos- 

 phates is probably derived from bones. According to the 

 researches of Carnot, there is often a considerable quantity 

 of calcium fluorid in bones and teeth. 32 In fossil bones very large 

 quantities have been found, reaching as high as 6.21 per cent, of 



30 Annales de Chimie analytique, 1898, 3 : 6. 



31 Annales des Mines, 1893, [9], 3 : 138. 

 31 Comptes rendus, 1892, 114 : 1189. 



Annales de Chimie et de Physique, 1855, 1 : 47. 



