72 DK. VINEN ON CYKIP3 QUERCUS-PETIOLI. 



On the Quantity of Tannin in the Galls of Cynips Quercus-petioli. 

 By Edward Haet Vinen, Esq., M.D., E.L.S. &c. 



[Read February 19th, 1856.] 



Much interest has been excited by the frequent occurrence in this 

 coujitry of the gaUs of Cynips Quercus-petioli, and they appear, 

 from a recent communication in the ' Gardeners' Chronicle,' to 

 have increased to such an extent during the past season, as to do 

 vast mischief to the trees infested by them, rendering them unpro- 

 ductive of acorns, and even threatening their entire destruction. 



In a recent conversation with Mr. Westwood on this subject, 

 he informed me that these galls had been used in Devonshire for 

 the purpose of making ink, and at the same time suggested that 

 it would be desirable to know whether they contained sufficient 

 tannin to render them useful substitutes for tlie ordinary galls of 

 commerce. At his request I imdertook to ascertain this, and 

 thought the residt might be sufficiently interesting to communi- 

 cate to the Society: the following is the result of my examination. 

 By macerating 100 grains of Devonshire galls in sether and water, 

 a residue was obtained weighing 26-74 grains : this contained 17 

 grains, or about two-thirds, of tannic and gallic acids. In order 

 to estimate the comparative value of these galls with those of 

 commerce, 100 grains of best Aleppo galls were submitted to the 

 same treatment with aether and water. The residue weighed 58*50 

 grains, containing 56 grains of tannic and gallic acids. Of the 

 superiority of the foreign galls there can of course be no doubt ; 

 but in comparing the results of these two analyses, it is necessary 

 to observe, that the Aleppo gaUs operated on were very heavy 

 specimens of the best kind of gaUs of commerce, and that they 

 had not been perforated by the Cynips, while the Devonshire galls 

 had all been perforated, and therefore contained a much smaller 

 proportion of tannin than would have been the case if they had 

 been examined at an earlier period. 



If we compare the published analyses of nutgaUs, considerable 

 difference wall be found in the quantity of tannin obtained by 

 different chemists. The following are the principal : — 



Sir Humphry Davy foimd . . 26 per cent, of "tannin." 



Pelouze 40 



Leconnel 60 



Guibourt 65 



Mohr 72 



Buchner 77 



