87 



other species. — F. v. M). Precipitate tlie aqvieous decoc- 

 tion with acetate of lead, filter, precipitate with snbacetate 

 of lead, decompose this second deposit with sulphuret of 

 liydrogen, filter ofl" from the siilphuret of lead, precipitate the 

 liquor Avith acetate of lead in order to remove the rest of citric 

 acid ; thi'ow down the filti-ate with snbacetate of lead, and decom- 

 pose the precij)itate with snlphnret of hydrogen; a solntion is 

 obtained of slightly bitter, styptic taste, imparting a beautiful 

 green colour to chloride of iron. 



Gallic Aci(l=Cu H3 O7 -|-3 HO-f 2 Aq. This acid is said to 

 exist in many vegetables, especially in those containing tannin ; but 

 as Gallic acid has not yet Ijeen obtained with certainty as decom- 

 position-prodiict from any iron-greening tannic acid, but only from 

 two ii'on-blueing tannic acids, i.e., from ordinary and Chinese nut- 

 galls, and fiom si;mach, it seems at least improbable, that Gallic 

 acid should occur i-eady formed in other plants than those named 

 already (and in species closely allied to them. — F. v. M.). 



In order to obtain the Gallic acid which may exist ready formed 

 in a vegetable extract, the always co-existing tannic acid is first 

 removed by means of glue, either dissolved in water, or better, in 

 the form of animal membrane (isinglass) soaked in cold water. 

 The liquid, after it has been sejiarated from the tannate of glue, is 

 evaporated to an extract, exhausted with strong alcohol, the solu- 

 tion evaporated again, and treated with ether. During the 

 evaporation of the etlier, the g-allic acid forms in crystals. — It 

 crystallises in white, silky needles, is inodorous, of an acidulous 

 styptic taste, decomposes at 210° under partial decomposition and 

 formation of a sublimate of pyrogallic acid^Cio HeOo ; fuses at 

 226°, dissolves in 100 parts cold and in 3 parts boiling water, 

 readily in alcohol, less leadily in ether; the aqueous solution throws 

 down neither glue nor alkaloids, but precipitates the salts of oxyd 

 of iron with a dark-blue colour, like that produced by gallotannic 

 acid; the gallate of iron (the above deposit) differs from the 

 tannate of iron by its gi-eat solubility in acetic acid and in the 

 hydrates and carbonates of alkalies (inch ammonia), while of the 

 tannate of iron only traces are dissolved by acetic acid, and the 

 iron tannate is decomposed completely by the hydrates and 

 carbonates of potash and soda, and partly by ammonia, in the 

 former case under formation of oxyd of iron. Only the gallates of 

 alkalies and of the alkaline earths are soluble in water. 



Gallotannic A cid =054 II22 O34. In certain excrescences on 

 the branches of a few plants, produced by the puncture of insects, 

 viz., in Turkish nutgalls (from Quercus infectoria), in Chinese 

 nutgalls (from Rhus semialata), and in the bark of the sumach 

 tree (Rhus coriaria), and some other species. It cannot be 

 decided at present, if it is still more widely distributed (see Kino- 



