GtTM ARABIC AND GUM ADRACANTH. £57 



acid ; but can be neither the oxalic, the tartarous, or the 

 citric, becaufe their combinations are infoluble in water, 

 and that betides they exift but in a fmall number of vege- 

 tables; ftill Iefs can it be the benzoic, the gallic, the morox- 

 ulic, or the honefiic, which are very rarely found in naturally, 

 and of which the three laft alfo form infoluble compound s. 



There only remains to decide between the acetous and the The acid mull 



malic acids, which are the mod abundant in the vegetable be f lther th , e 

 " . ° acetous or the 



kingdom. The firft forms, as is well known, foluble com- malic. 



binations with all the fubftances with which they are capable 



of union ; fome of them are even deliquefcent. It is betides 



the mod frequent refult of the operations of nature in the 



vegetable and animal fyftems, fince it is formed by vegetation, 



by fermentation, the acVion of the more powerful acids, and 



by the influence of heat. 



The combinations of the fecond are for the mod part in- But the malic 



foluble in water; that which it forms with lime particularly / orms infolub ! e , 

 . . compounds witra 



is not fenfibly foluble, but when there is an excefs of acid ; lime, 



and its exigence in nature is by no means fo frequent as that 



of the acetous acid ; and as the lime which is found in the 



tranfparent gums has been inconteftibly dilTolved in the juices 



of the vegetables which produce thefe fubftances-, it is much confequently the 



more probable, that this earth is in them combined with ]ikel ce ^ s< y 



acetous acid than with any other. 



It is alfo probable, that the fmall quantity of potafh which Thepotam in 



I found in the aflies of the burnt gums, is united to the fame gums a!fo forms 



\ an, acetite* 



acid, which explains why thefe fubftances are fo fenfible to 



humidity, and foften fo much as to prevent their pulveriza- 

 tion. 



I am, however, much inclined to think, that in certain Some gums con- 

 opaque adracanth gums, which are of difficult folution, and grMteTpiJr'or- 

 yield much lime on incineration, this earth is combined with tions. 

 malic acid. I have had occafion lately to examine a gum 

 gathered by' M. PalilTbt Bauvois, from the cochineal nopal, 

 which was opaque, fwelled with water, did not diflblve 

 uniformly, and which yielded eight per cent, of lime. And 

 as the fap of every cactus which I have analyzed, yielded 

 more or lefs acidulous malate of lime, there is great reafon to 

 believe, that the fpecies of it which nourifhes the cochineal 

 contains it likewifc : and that it is the prefence of this fait 

 proceeding from the vegetable, and diflblved in the fap along 



Vol. XII.— December, 1805. S with 



