Anal;ifts of the Mellite, of Homgjleitt. 519 



From the refult of thefe experiments we fee, that the acid of the honigftein has many 

 properties analogous to thofc of the acid of forrel, and by the comparifon I have made, I 

 have perceived no difference but the following : i . The precipitate which it caufes in the 

 folution of fulphate of lime is lefs fpeedily manifefted, and is cryftalline, inftead of being 

 pulverulent, like that which is formed by the acidulous oxalate of pot-afli. 2. It appears 

 lefs acid to the tafte than the acidulous oxalate of pot-a{h ; but this may depend upon my 

 not having added enough of nitric acid to the combination with pot-afli, to deprive it of a 

 fuflicient quantity of the alkali ; and 3. It fwells up rather more by heat than the acidulous 

 oxalate of pot-afli. 



In other refpeds the fublimed fait, the great quantity of carbonic acid, and the little 

 coal which the mellite affords by djfVillation, are fads that feem to unite in proving the 

 identity of the two acids : for the habitude of the fait of forrel by fire is the fame *. 



The o£tahedral figure of the honigftein appears alfo to have analogy with that of the 

 oxalic acid, which is a re£tangular prifm terminated by pyramids with four faces. It is 

 only necefTary to examine the inclination of thefe faces in order to obtain a certainty. 



Neverthelefs, as I have had no more than about 1.34 gramme of this acid at my dif- 

 pofal, I have not been able to fubjedi it to all the trials which would have been required 

 to demoulhate in the moft abfolute manner its identity in all refpefts with the oxalic acid". 

 For though they have prefented fimilar phxnomena in all the comparative trials I hare 

 made, it is poffible that by other that might yet be made^ there might be found a fingle 

 difference which would deftroy the fimilitude. 



It is therefore chiefly with a view to engage the chemifts of Germany, where this fub- 

 ftance is more common, to recommence the analyfis of honigftein, and to compare its acid 

 In every poflible refpeft with thofe of forrel that I publifh this notice. 



If my opinion fhould be confirmed by new experiments, we fliali then poffcfs the oxalid 

 acid in all the three kingdoms ; namely, in the ftate of acidulous oxalate of pot-afli in fe- 

 veral kinds of vegetables; in that of oxalate of lime in the human urinary calculi; and 

 laftly, in the ftate of oxalate of alumine in the bowels of the earth among bitClminous 

 wood. But in whatever part it is found, it appears to owe its origin to vegetable fub- 

 ftances. 



'Note, Since the above notice was drawn up, I have thought of mixing the acid of ho- 

 nigftein combined with a fmall quantity of pot-afli, with a folution of pure fulphate ot 

 alumine, and a very abundant ilocculent precipitate was immediately afforded. On the 



• The acid of forrel, or oxalic acid, is that which affords by diftillation the largeft proportion of carbonic 

 acid and water, becaufe it contains more oxigen than any other known vegetable acid, 



4 Other 



