34 HENRY G. SMITH. 



belonging to this class, all gave identical results with the 

 above when fused with caustic potash. 



Astringency values of the kinos. — After several trials the 

 following method was adopted, and the values taken on the 

 air dried kinos of nearly 100 species of Eucalyptus. The 

 astringency value of some of these is very low, but these 

 will be dealt with in a subsequent paper. The following 

 solutions were prepared : — 



1. Indigotin 5 grams and sulphuric acid 50 grams per 



litre, and filtered through paper before using. 



2. Potassium permanganate 1 gram per litre. 



3. Kino (carefully picked) 1 gram per litre. 



4. Gallo-tannic acid 1 gram per litre. 



5. Standard colour solution. 



The kinos were dissolved by heat if necessary. 10 cc. 

 of the kino solution was added to 20 cc. of the indigotin 

 in | litre of water contained in a large beaker, and titrated 

 with the permanganate. The end reaction was best deter- 

 mined by placing a beaker alongside, of the same size as 

 the one containing the tannin, and holding the same amount 

 of liquid which was coloured to the exact yellow-green 

 tint given by the indigotin solution when changing from 

 the greenish tint to the yellowish one. This tint was easily 

 adjusted by using the green solution obtained by boiling a 

 few drops of alcohol with potassium dichromate solution, 

 together with a solution of potassium chromate. The 

 titration was carried out before a window with a good light, 

 and the end reaction determined by looking through the 

 liquids towards the light ; one drop of permanganate was 

 sufficient at this stage to bring about a readily detected 

 change of colour. The permanganate was always added 

 in the same manner. The astringency value of gallotannic 

 acid containing 14*43 /° water was taken as 1000, and on 

 this basis the following results were obtained : — 



