9fi 



Mr. Dtry»« 



ffundard pot' 

 ash. 



eoiabiii«d 



-with bo rack' 

 •cid without 

 •Tolution of 

 water. 



Common pot. 

 ash does not. 



Combustion of 

 potassium in 

 oximuriatic 

 gai. 



DiffiererT'e be 

 tween the 

 pure alkalis 

 andiheirhi- 

 tfrates. 



Fercxides of 

 potash and 

 •«da. 



OV THB NATCR* Of POTASSrUM AND SOpIUM. 



an etperiment on the action of silex on this hidrate^has con- 

 cluded in his Bakerian lecture for 1809, that it contains, 

 taking the potash formed by the combustion of potassium as 

 a standard, about l6 or 17 per cent. 



In the same lecture he has shown from the quantity of 

 fused muriate, produced from a j^iven weipjht of potassium 

 in muriatic acid gas, that his standard potash has a much 

 greater saturating power, than the hidrate of potash ; that 

 XOO of the former wiil neutralize the same quantity of acid 

 »s 120 of the latter. 



He has since ascertained, that, when potassium and 

 powdered boracic acid glass are heated together in a tube of 

 plat'ma, both with and without red oxide of mercury, no 

 water or inflammable gas is produced; and that the result 

 is the same, when potash formed by the combustion of po- 

 tassium is combined with boracic acid. 



On the contrary, substituting the hidrate, or common 

 fused potash, he has in one experiment actually collected 

 about 15 per cent of water; and the loss of weight after the 

 combination of the acid and alkali, in other similar experi- 

 raents, indicated from 15 to 20 per cent. 



He haa found too, that the only product of the combus- 

 tion of potassium in oximuriatic gas is fused muriate of pot- 

 ash ; that the same salt is fotraed ; and oxigen gas evolved,* 

 without the least appearance of water, when potash from the 

 combustion of potassium is used ; and that water as well as 

 oxigen is separated when hidrate of potash is employed. 



In addition to these circumstances, which are stated in Mr. 

 Dary*slast Bakerian lecture, a copy of which he has allowed 

 me to peruse, there are physical properties also pointed out, 

 distinguishing potash and soda from the hidrates; the former 

 for instance, require a much higher temperature for fusion 

 than the latter, and possess greater hardness and apparently 

 greater specific gravity. 



It is Weil known to those who have attendefl to the l^te 

 progress of chemical discovery, that potash and soda are only 

 to be procured by the rapid combustion of the alkaline 

 metals, or by the after application of a red-heat; and that per- 

 oxides are formed whe^ the combustion is feeble either in 

 «xigen gas or common air. Messrs. Gay-Lussac and The- 

 . . ' nard 



