MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 405 
reaction proves that these substances have a similar composition, and forms perhaps 
the most characteristic mark of distinction between them and rubianic acid. Rubi- 
hydran is not precipitated from its aqueous solution by any reagent except basic 
acetate of lead, which produces a light brownish-red precipitate, which is paler and 
less bright than the precipitates produced by the same reagent in solutions of rubian 
or rubidehydran. The liquid filtered from this precipitate has still a light yellow 
colour, and ammonia produces in it a fresh precipitate of a pale pink colour, after 
which it appears colourless. Rubihydran is soluble in alcohol, but not very easily. 
From the manner in which it is prepared it may be inferred, that it is incapable of 
yielding rubianic acid by the influence of the same agents which lead to the formation 
of the latter from rubian. In order to obtain this substance in a perfectly dry state, 
it is necessary to heat it in the water-bath continuously for a day or two. In two 
analyses I obtained numbers corresponding respectively vvith the formulas €581145041 
and C56H42O38. I only succeeded once in obtaining it of the same composition, or 
as free from water as when in combination with oxide of lead. On this occasion it 
gave the following results : — 
0'3940grm. gave 0‘7440 carbonic acid and 0’2130 water, numbers which lead to 
the following composition : — 
Carbon . . . 
Eqs. 
. 56 
336 
Calculated. 
51-29 
Found. 
51-50 
Hydrogen . . 
. 39 
39 
5-95 
6-00 
Oxygen . . . 
. 35 
280 
42-76 
42-50 
655 
100-00 
100-00 
On being burnt this specimen left no ash. 
The lead compound was prepared by dissolving the substance in alcohol and then 
adding acetate of lead and ammonia, taking care to leave an excess of rubihydran in 
solution, filtering, washing the precipitate with alcohol and drying-, at first in vacuo, 
and then for several hours in the water-bath. 
I. 0-8740 grm. of this compound gave 0-6720 carbonic acid and 0-1970 water. 
0-7270 grm. gave 0-5850 sulphate of lead. 
If. 0-8860 grm. gave 0-6820 carbonic acid and 0-1930 water. 
0-8465 grm. gave 0-6805 sulphate of lead. 
In 100 parts ; — 
Carbon .... 
I. 
. . 20-96 
II. 
20-99 
Hydrogen . . . 
. . 2-50 
2-42 
Oxygen .... 
. . 17-34 
17-44 
Oxide of lead . 
. . 59-20 
59-15 
100-00 
100-00 
The amount of oxide of lead here stands in no simple relation to that of the other 
