PROXIMATE PRINCIPLES OF SOME OF THE LICHENS. 
73 
liad similar properties, and when subjected to analysis gave identical results. I 
regret to add that in all my analyses, amounting to about a dozen, I always obtained 
about one and a half per cent, less carbon than Mr. Schunck, though the combustions 
were made with all possible care, and a stream of oxygen gas was sent through the 
apparatus towards the close of the opei-ation. The alcoholic and aqueous solutions 
of erythric acid do not redden litmus paper, its acid properties are therefore rather 
feeble. Erythric acid agrees with (alpha) and (beta) orsellic acids in yielding red- 
coloured compounds with ammonia, and also in its reaction with hypochlorite of 
lime. There is, generally speaking, a great similarity among these bodies in their 
behaviour towards reagents ; still their atomic weights and the products of their 
decompositions are very different. 
I. 0'5951 grm. acid dried at 212° Fahr., gave with chromate of lead T2404 Co,, 
and 0-298 HO. 
II. 0-3846 grm. gave 0 8031 carbonic acid and 0-1846 water. 
III. 0-6/37 grm. gave 1-4115 carbonic acid and 0-3415 water. 
Calculated numbers. 
I. 
11 . 
III. 
C 20 1528-7000 
57-34 
56-85 
56-94 
57-14 
Hll 137-2745 
5-15 
5-56 
5-33 
5-63 
0 10 1000-0000 
37-51 
37-59 
37-73 
37-23 
2665-9745 
100-00 
100-00 
100-00 
100-00 
These analyses give C .20 H^^oOy+HO for the formula of hydrated erythric acid. 
I made repeated attempts to form the lead salt, but I could not obtain it of a con- 
stant composition. I had no better success with an attempt to form a baryta salt. 
When erythric acid was dissolved in an excess of baryta in the cold, and a stream of 
carbonic acid gas sent through the solution, the whole of the baryta was thrown 
down in the state of carbonate. This plainly shows that erythric acid is a much 
feebler acid than either of the orsellic acids. 
Erythric Ether. 
Erythric ether may be readily obtained by boiling the crude acid in strong spirits. 
It is crystallized out of water and purified in the same way as orsellesic and lecanoric 
ethers, which substances it very closely resembles in appearance and properties. 
I. 0 4646 grm. ether dried at 212° Fahr., gave T032 carbonic acid and 0 265 water. 
II. 0-372 grm. substance gave 0-8285 C 02 and 0-2115 water. 
Calculated numbers. 
I. 
II. 
24 C 1834-440 
6 O- 7 O 
60-65 
6 O -74 
15 H 187-192 
6-19 
6-33 
6-31 
100 1000-000 
33-11 
33-02 
33-05 
3021-632 
100-00 
100-00 
100-00 
The rational formula for erythric ether therefore is Cgo HioOyd-C, H 5 O, 
MDCCCXLVIII. 
L 
