‘. 
_» ash, chlorate of potash, nitrate of ammonia, chlorid of potassium 
me ae —— 4 ne. 
108 .— cae “Scientific Intcthensthe 
These relations are bth observed when dilute noma of the salts are 
diffused from the solution-cell, such as 4, 2 or even 1 per cent. of salt. :* 
. The ee diffused in the same time from 41 per coli soiakonehinal A 
the three salts, carbonate of potash, sulphate of potash, and sulphate ‘of 
ammonia, were 10-25, 10°57, and 10°51 grains respectively ; and a sim-. ; 
ilar approach to equality was observed in the 1, 2, and 62 per cent. so- * 
lutions of the same salts. It also held at different temperatures. 2 
acetate of potash appeared to coincide in diffusibility with the same an 
~ group, and so did the ferrocyanid of potassium. ‘The nitrate of pot- s 
ch 
Brae 
and chlorid of ammonium formed another equi-diffusive group. Cn. 
times in which an equal amount of diffusion took place in these two 
groups appear to be as 1 for the second to 1:4142 for the first, oras 1. 
to the square root:o ow in gases, the squares of the times of ~-; — 
equal diffusion are the ‘densities of the gases. The relation between 
the sulphate of potash and nitrate of pa groups would therefore fall, | 
to be referred to the diffusion molecule or diffusion vapor of the first. - . | 
= al 
group having a density represented by 2, while that of the second group ~ 
is represented by 1. 
The corresponding salts of soda appeared to fall into a nitrate and _ 
sulphate group also, which have the same relation to each other as the ’ 
potash salts 
The relation of the salts of potash to those of soda, in times of equal. 
diffusibility, appeared to be as the square root of 2 to the square root 
of 3; which gives the relation in density of their diffusion molecules, 
as 2to 3. Hydrate of potash and sulphate of magnesia were less fully é 
f thene times are all. uared, the following remarkable ratios 
ent salts, each of which is the type of a class of salts, hydrate of pot- 
ee 1, nitrate of potash 2, sulphate of potash 4, sulphate of magnesia 16, 
with nitrate of soda 3, and sulphate of soda 6. 
In conclusion, it was observed, that it is these diffusion molecules of 
the salts which are concerned in solubility, and not the Daltonian atoms 
er equivalents of chemical combination; and the application was indi- 
cated of the sip lice of the diffusibilities of different substances to 
proper study of endos 
2. On the pate ae of Formic Acid in Stinging Nettles ; by Dr. 
Gorvur-Besanez, (Journ. fiir Prakt. Chem., xlviii, p. 191; Chem. Gaz., 
Jan. 1, 1850, p. 8.—Some time ago, F. Will showed, by microghemi- 
cal and microscopical experiments, that the fluid in the hairs of the so { 
called nope g -caterpillar (Bombyx processionaria), which causes an 
in = mation of the skin, as well as the liquid in the poisonous or- 
of some insects, is nothing else than formic acid. It became 
highly salads therefore that formic acid would also occur in the veg- 
etable kingdom already formed; and the first class of plants which 
bout a pound of the collected plants Urtica urens and dioica, was 
cut small and pressed, and submitted ps ‘istillation with about four times 
the quantity of water and a few drops of concentrated sulphuric acid. 
