214 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



TANNIN IN CLOVES. 



By W. HODGSON ELLIS, >I.A., M.B. 



(Read before the Canadian Innfitvte, -Xov. 27, 18H0.) 



Some time ago, while examining cloves adulterated with fai'inace- 

 ous matter, I was struck by the fact, that in testing for starch with 

 solution of iodine, it was necessary to add a considerable quantity of 

 iodine before a blue colour appeared. The quantity of iodine required 

 could even be used as an appx'oximate measure of the quantity of 

 pure cloves in the sample. Some preliminary ex[)eriments led me to 

 attribute this action to tannin, and I made, with the assistance of 

 Mr. F. T. Shutt, a number of determinations of tannin in pure 

 ■cloves by means of Lbwenthal's process. 



Our manner of working was as follows : — 2 grms. cloves were 

 exhausted by boiling under an inverted condenser, filtered, and the 

 filtrate made up to 500 c.c. ; 50 c.c. of the filtrate was then titrated 

 with a solution of permanganate (1 grm. to the litre). In 100 c.c, 

 of the filtrate the tannin was pi'ecipitated by gelatine and acid salt 

 solution, made up to 250 c.c. filtered, and 50 c.c. titrated with per- 

 manganate. Indigo cai'mine was used as an indicator. The titration 

 was carried out in a porcelain basin. The liquid operated on was 

 diluted to about 750 c.c, and tlie permanganate was allowed to run 

 into the basin at about the rate of one drop in a second, with con- 

 stant stirring. The method was essentially that described by Proctor 

 (Chem. News, xxxvi., 58). 



AVe then made determinations of tannin in clove stems and in all- 

 spice. I have subsequently, with the assistance of Mr. F. W. 

 Babington, made a number of similar deternunations in commercial 

 cloves and allspice, both pure and adulterated. The following table 

 gives our results, stated in c.c. decinormal permanganate, required to 

 oxidize one gram of cloves before and after the precipitation of the 

 tannin. In calculating these results to tannin, I have used 

 Neubauer's factor, viz., 6.3 grm. oxalic acid will require for oxidation 

 as much permanganate as will oxidize 4.157 gx'm. gal lotannic acid. 

 The solution of permanganate used was titrated against oxalic acid 

 and checked by pure tannic acid. In using this factor I do not, of 

 •course, intend to assert that the tannin of c-loves is identical with 



