at Lemington Prior?* 265 



Jtttle muriatic acid is carried up in like manner when this i3 

 tifed to extricate the hepatic gas. We may farther conclude, 

 that though the remark of Bergman on the effect of the 

 prufliat of potafh is true ; the remark which accompanies it 

 (on the colour produced by infufion of galls) is erroneous. 

 A purple colour is always, I believe, occafioned by extra- 

 neous acid ; in which cafe the pruffiat of potafh is alfo pre- 

 cipitated. From the fame facts we are enabled to detect 

 another error alfo, into which the fame great man has been 

 betrayed. In his analyfis of the acidulous waters of Medvi, 

 in Oftro-Golhland [Bergman's EJfays, Dijfertation Till. 6.), 

 he has noticed a refiduum of 4^ grains of iron, diffolved 

 partly by hepatic gas, partly by carbonic acid. Now we 

 have feen that there is no decompofition of thefe liquors by 

 boiling ; nor does any oxyde precipitate, how long foever 

 the evaporation be continued. The hepatic gas feems to 

 be totally decompofed : nitric acid dropped into thefe li- 

 jquors precipitates nothing. 



Are we then to conclude with Mr. Kirwan, that hepatic 

 gas does not decompofe iron or any other metal ? As the 

 gas ilfelf is decompofed, this, in ftridt propriety of language, 

 muft be allowed to be true ; but that fome folution is 

 effected during the decompofition the following remarks 

 evince. 3. A piece of clean and bright iron was put into 

 fome of the hepatifed folution (if I may be allowed fo to 

 call it, while its true compofni' n is unknown) : it foon be- 

 came turbid; a copious ochry precipitate fell down ; and 

 in 24 hours the whole furface of the iron was covered with 

 ruft. 4. Let the folution be boiled in a copper veffel, a 

 precipitate alio feparates of an ochry colour ; but it is fmall- 

 er in quantity than in the former experiment. 5. Digeft a 

 piece of clean iron in the fo'ut on after it has been boiled in 

 a copper veffel ; much ochry matter Mill feparates ; but there 

 is no veftige of metallic copper on the iron plate. 6. Di- 

 geft copper filings in the liquor in which iron fiungs have 

 been previoufly digefted ; feparate the copper filings, and 



now 



