396 
MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 
is entirely removed from its solution by hydrate of alumina, to which it communicates 
a light red colour, and also by hydrated peroxide of iron, though not so easily as by 
alumina. Rubianic acid dissolves easily in a boiling solution of perchloride of iron, 
forming a dark greenish-brown liquid, which contains protochioride of iron. The 
solution deposits nothing on standing, and on evaporation only a small quantity of 
black powder separates, which is probably a compound of alizarine and oxide of iron. 
Acetate of copper gives in watery and alcoholic solutions of the acid a brownish-red 
precipitate, which is soluble in boiling acetic acid. Neutral acetate of lead turns the 
watery solution of the acid red, but produces no precipitate; basic acetate of lead, 
however, gives a copious red flocculent precipitate, just as in a solution of rubian. 
An aicoliolic solution of the acid gives with an alcoholic solution of acetate of lead a 
light red precipitate, which after filtration of the alcoholic liquid dissolves in pure 
water. On adding nitrate of silver to an aqueous solution of the acid and boiling no 
change takes place, but on the addition of a few drops of ammonia a dark reddish- 
brown precipitate slowly subsides as a fine powder, which is soluble in an excess of 
ammonia, forming a red solution, which does not change, and shows no signs of any 
reduction taking place when it is boiled. On adding chloride of gold to a watery 
solution of the acid no change takes place even on boiling, but on the addition of a 
little caustic alkali metallic gold is deposited, partly as a brown powder, partly in 
shining scales. If rubianic acid be mixed with water to which a quantity of erythro- 
zym has been added, the yellow crystals of the acid gradually disappear, and are 
converted into alizarine. The liquid is found to contain sugar. 
It is impossible to dye with rubianic acid. Mordants acquire in boiling solutions 
of the acid no more colour than in solutions of rubian or rubianine. 
On submitting the acid to analysis the following results were obtained : — 
I. 0*4605 grm., formed by the action of bicarbonate of baryta on rubian, dried in 
the water-bath and burnt with chromate of lead, gave 0*9445 carbonic acid and 
0*2250 water. 
II. 0*4030 grm, of another preparation, obtained by the action of bicarbonate of 
baryta, gave 0*8240 carbonic acid and 0*2020 water. 
III. 0*2750 grm., formed by the action of caustic soda on rubian, gave 0*5605 car- 
bonic acid and 0*1390 water. 
IV. 0*4750 grm., obtained by means of ammonia, gave 0*9670 carbonic acid and 
0*2295 water. 
V. 0*2920 grm., obtained by means of caustic lime, gave 0*6000 carbonic acid and 
0*1490 water. 
These analyses give in 100 parts — 
Carbon . . 
I. 
. . 55*93 
11 . 
55*76 
III. 
55*58 
IV. 
55*52 
V. 
56*04 
Hydrogen . 
. . 5*42 
5*56 
5*61 
5*36 
5*66 
Oxygen . . 
. . 38*65 
38*68 
38*81 
39*12 
38*30 
