418 Dr. Stenhouse o7 some 
blue, and acids gray or green. A few experiments which I 
have made have, however, given somewhat different results 
from those of Cavallius. 
A solution of the tannin of catechu was prepared by mace- 
rating a large quantity of catechu in a very little cold water ; 
it was therefore quite free from catechin. A portion of this 
solution was allowed to remain for some days in contact with 
a quantity of iron chips; it assumed a dirty, grayish black co- 
lour, which, however, did not at all resemble the blue-black 
colour which nut-galls, oak, bark, &c. exhibit when similarly 
treated. The precipitate did not become green when a little 
acetic acid was added to it, but it dissolved in an excess of 
acid, and on being neutralized with ammonia a purple gray 
precipitate appeared. ‘Tannin of catechu gave a dull grayish 
black precipitate with acetate of iron. With neutral acetate 
of lead it gave a light yellow precipitate, which on the addition 
of sulphate of iron assumed a dark gray colour, much lighter 
than the preceding. Basic acetate of lead gave similar results, 
Chloride of iron gave an olive green; perchloride an olive 
brown, and protonitrate a yellowish green precipitate. Tan- 
nin of catechu, when treated with acetic acid and sulphate of 
iron, gave a dark olive precipitate. 
The tannin of larch bark, which gives a light green preci- 
pitate with protosulphate of iron, gave with acetate of iron a 
purplish black precipitate, which on standing for a day or so 
assumed a dark lead colour. When treated first with acetate 
of lead and then with sulphate of iron it gave a grayish purple 
precipitate. When mixed with a little acetic acid it gave a 
dark gray precipitate on the addition of sulphate of iron. 
Chloride of iron produces a grayish brown, and nitrate of iron 
an olive brown precipitate. 
The tannin of gum kino gave with protosulphate of iron a 
dark green, and with acetate of iron a purplish black precipi- 
tate, which on standing changed to grayish black. With pro- 
tochloride and protonitrate of iron dark green precipitates, 
which quickly changed to grayish brown. The effect of alka- 
lies on all these precipitates was only to deepen their colours, 
but not to change any of them bluish black. 
The tannin of alder bark, birch bark and tormentil root, 
gave purplish black precipitates with acetate of iron, which 
however on standing became grayish black, and their reac- 
tions with the inorganic salts of iron were almost identical with 
those of kino, catechu and larch bark, and wholly dissimilar 
with those of galls, sumach, valonia, &c. Very good ink of a 
bluish black colour may be made from nut-galls, oak bark, 
sumach, valonia, divi-divi, &c.; but the tannin of catechu, 
