400 
MR. STENHOUSE ON THE EXAMINATION OF THE 
cautions are requisite, which I shall shortly describe. Erythromannite in the state 
of powder is to be slowly added to a quantity of fuming nitric acid kept at a low 
temperature. The erythromannite rapidly dissolves, while considerable heat is 
evolved. So soon as a complete solution is effected, rather more than an equal bulk 
of sulphuric acid must be cautiously added to the solution. When the mixture has 
stood for half an hour, it becomes filled with a magma of crystals. These are collected 
in a funnel stopped with asbestos, and are left to drain. They are next washed with 
cold water, in which they are insoluble, till all adhering acid is removed, and then 
dried by pressure between sheets of blotting-paper. The compound is then boiled 
with moderately strong spirits, in which it readily dissolves, and on the cooling of 
the liquid it is deposited in large flat crystals resembling those of benzoic acid, only 
larger, and exhibiting a great deal of a mother-of-pearl lustre. 
It might naturally be supposed that this compound would also be formed by dis- 
solving erythromannite in a mixture of equal parts of fuming nitric and sulphuric 
acids, and that it would be thrown down by adding a sufficient quantity of water. 
This is not the case, however, either with it or with the mannite compound, which 
can only be procured in the way already described, by employing the nitric acid first, 
and precipitating the nitrated compounds by adding the sulphuric acid afterwards. 
The solutions of nitrated erythromannite are quite neutral to test-paper. When 
nitrated erythromannite is heated to 61° C. it melts, but recrystallizes immediately 
when cooled a few degrees below that temperature ; when strongly heated, it takes 
fire and burns with a gentle deflagration. When, however, the dried erystals are 
mixed with a little sand and are struck with a hammer, they detonate with great 
violence. This reaction clearly shows the close analogy that subsists between nitrated 
erythromannite and quintonitrated mannite, which will appear still more distinctly 
on comparing the results of their analysis. As however this relation equally subsists 
between mannite and erythromannite, I shall first subjoin the formulse and analyses 
of these two bodies also, so that the intimate relation existing among these four 
compounds may be rendered more distinctly perceptible. 
0'4702 grm. erythromannite, dried in vacuo and ignited with chromate of lead, gave 
0'679 carbonic acid and 0*355 water. 
Erythromannite . 
per cent. 
Found. 
Mannite. 
per cent. 
lie 825 
39*29 
39*36 
C 12 900*0 
39*57 
14 H 175 
8*33 
8*60 
H14 174*7 
7-67 
no 1100 
52*38 
52*04 
0 12 1200*0 
52*76 
2100 
100*00 
100*00 
2274*7 
100*00 
The rational formula of mannite is Hi4 0 |2' 
The rational formula of erythromannite is 
Mannite therefore only differs from erythromannite by containing one equivalent 
more of carbonic oxide. 
