336 Dr. Stenhouse's Examination 



quantity of a species of tannin which gives bluish-black preci- 

 pitates with the sulphate, nitrate and chloride of iron, and a 

 bluish-purple precipitate with the acetate. It is also readily 

 precipitated by gelatine, but not by tartar-emetic. This tannin 

 is mixed with a small quantity of gallic acid. The shell of 

 the fruit also contains a good deal of a fatty matter, which is 

 solid at ordinary temperatures and crystallizable. It is easily 

 saponified when boiled with an alkali, its compound with soda 

 crystallizes in large scales. This fat contains an acrid sub- 

 stance which vesicates, but it contains no sulphur. When 

 the fat is first expressed from the nut it is but slightly co- 

 loured, but by exposure to the air it becomes first brown 

 and then black, and loses much of its acrimony. 



Pomegranate Rind. — The rind of the pomegranate contains 

 a considerable quantity of a species of tannin which precipi- 

 tates gelatine copiously, but gives only a very feeble precipi- 

 tate with tartar-emetic ; with protosulphate, chloride and 

 nitrate of iron, it gives precipitates which are at first deep 

 blue but almost immediately change to very dark olive. With 

 acetate of iron it gives a purple precipitate. Reuss, who has 

 made an analysis of pomegranate rind, states that he found it 

 to contain a little gallic acid. I have been unable to find any, 

 though I have sought it very carefully. 



LarchBark. — The bark of the larch is employed in Scotland 

 to some extent in tanning. The quantity of tannin it contains 

 is considerable, but the leather made with it is of inferior 

 quality. The aqueous solution of the bark is strongly acid 

 to test paper, and has at first a pale yellow colour, which ex- 

 posure to the air renders brownish-red ; it gives a copious 

 fawn-coloured precipitate with gelatine, but none with tartar- 

 emetic. With the sulphate, chloride and nitrate of iron, it 

 gives olive-green precipitates. Acetate of iron throws it down 

 of a bluish-purple colour. Sulphuric acid precipitates it of 

 a reddish-yellow colour. When boiled with the acid it dis- 

 solves, and the liquid assumes a fine scarlet colour like the 

 infusion of Brazil wood. The altered tannin precipitates on 

 cooling in beautiful red flocks, as it is but little soluble in cold 

 water. It is very soluble in alcohol and alkalies, and its solu- 

 tions have a rich scarlet colour, which is the most character- 

 istic reaction of this species of tannin. Larch bark also con- 

 tains a good deal of mucilage and resinous matter. Birch 

 bark, alder bark, and tormentil root, contain all of them con- 

 siderable quantities of tannin, which closely resemble that of 

 larch bark. All these species of tannin are readily precipi- 

 tated by gelatine, but not by tartar-emetic. They give olive- 

 green precipitates with most of the salts of iron except the 



