OBSERVATIONS ON MURIATIC ACID. 183 



gaged from the bads; but, as the heat requifite to diftil the 

 acid is more than (ufficient to decompofe it, oxigenized muri- 

 atic acid comes over with it; and oxigen gas is collected in the 

 pneumatic tub. If the diftillation be continued, the fame dan- 

 ger arifes a$ in the former cafe, becaufe the fulphuric acid be- 

 comes concentrated ; and it would feem, that its aclion upon 

 the fait is flight and partial at a low temperature, but violent 

 and inftantaneous when heated and concentrate. I could not, 

 therefore hope, by thefe means, to obtain the acid difengaged 

 and pure. 



If the manner of bringing the fulphuric acid and the fait into The fait added 

 contad be reverfed, and the fait be dropped into the acid, the to the ac,d ' 

 yellow vapours and the orange-coloured liquor are produced, 

 but generally without decrepitation. If they be aliowed to 

 remain fome days in contact, the vapours continue, and oxigen 

 gas is conftantly difengaged, even in the common light of the 

 day, and at the temperature of the atmofphere. By cooling the 

 firft receiver with ice, I thought that I had once obtained this 

 acid cryftallized in the form of four-fided pyramids, of an 

 orange colour. But, though I really believe this to have been 

 the cafe, I do not politively affirm it. 



Nitric acid produces nearly the fame phenomena ; but the Nitric acid ap. 

 fmell and other properties are rather lefs diftincl and marked, p e ' 

 than with fulphuric acid. 



Muriatic acid decompofes this fait, and unites to its bafis ; Muriatic acid, 

 but neither the yellow vapours, nor the orange-coloured liquor, 

 are produced. The c i re um fiances which attend the contact of 

 the acid and the fait, are as follows. If no more muriatic acid 

 b.e prefent than is merely neceffary to decompofe the fait, I do 

 not doubt that hyperoxigenized muriatic acid will be driven off, 

 as little decompofed as with the other acids, fuppofing the aclion 

 to be inftantaneous ; but, during the contact of thefe two bodies, 

 the acid expelled muft meet muriatic acid not yet combined, 

 and, uniting with it, always forms a portion of oxigenized mu- 

 riatic acid. The quantity of the laft acid muft vary, according 

 to the quantity of muriatic acid employed, and not combined 

 with the alkali. It was by this method that. Mr. Cruickfhank 

 obtained the muriatic acid gas, which he ftated to contain 

 4-3,5 per cent, of oxigen. 



Phofphoric and arfenic acids do not act upon this fait, till ^HofpK- and ace- 

 Heated with it ; and then much oxigen gas is eyolved. Thefe, gag^iee'r^by 



therefore, heat* 



