DECOMPOSITION OF PHOSPHATES BY CHARCOAiir 



2S1 



,\)\oy a degre£ of heat high enough, a sufficient quantity of 

 seed, and all the precautions I have mentioned above, I 

 have reason to think for instance, that, if the degree of heat 

 requisite to disengage the: phosphorus be employed at the 

 commencement of the operation, this product v;iil not be 

 obttiined separately, because it would combine v.jth the hi- 

 drogen gas of the coal. 



The coal of wheat, treated with boiling water before tlie The coal of 

 extraction of the phosphorus, yields a lixivium that turns ^^^^^^^^^j^*'^^"' "°* 

 sirup of violets green, and is indebted for this property to. phosphoric 

 potash. In this instance therf'fore the phosphorus appears ^^^'^j^'|r'°'^* 

 not to be owing to the action of the charcoal on free phos- uioala. 

 phoric acid. Neither does it arise from the decomposition of 

 phosphate of ammonia ; for the heat requisite to carbonize 

 the seed appears to be niore than suirici<;nt to volatilize this 

 salt. 



As I found a considerable quantity of phosphate of potash Considerable 

 in all tl)e ashes of the seeds I have analysed, particularly in ^"^^ntuy of 



1 , ^, • , T • • • »T • V phovphaieof 



wheat (see my Chemical inquiries concerning V egetation), potash obtai.w 



I thought it necessary to examine, v<hether this salt be de- ^^ ''°"' ^'^ 



composable by charcoal. 1 confess however it is not certain^ 



that this phosphate exists .already formed in the coal made 



in close vessels; for the water with which it was lixiviated 



afforded me none, or at most scarcely perceptible traces of 



this salt; but the coal, from its great porousness, retains 



substances interuiingled with it so pertinaciously, that we 



can conclude nothing from this operation. -: 



Sect. 2. Decompisitiun of the Phosphate of Potash by Char- 

 coal. 



Among the neutral pliosphates we know only Ihe phos- PiiObpliaie^r-- 



phate of ammonia, and those of some metals, that are-,de- ^""''"^'"■'"'^'^ -i' 



111 I 1 1111 1 • 11 chaicoLil. 



composable by charcoal. All the chemists who have en- ,,., 



•^ . J hose of pot- 



gaged m these inquiries have a&^:erted, that phosphate of jjsh, ^ofla, aid 



potash, phosphate of soda, and phosphate of lime. wiiKout '""'■'» ^"l^i'"^'^'^ 

 excess of acid, resisted this decomposition. It is on a sup- 

 position therefore, that these authors might have been misr 

 taken, that I made the following experiment. j 



I neutralized pure potasli with phospiioric arid prepared Phosphate .<>fr. 

 the action ^;f nitric acid on [ihosphorus. To p-.eveiit ajkl p''|'t^'^(]*..'^^|,'^' 



su'-'.Jici'Mi >'-'-' 



