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XX. Additional Observations on the Diffusion of Liquids. {Third Memoir.) 
By Thomas Graham, Esq., F.R.S., F.C.S. 8^c. 
Received March 27, — Read May 22, 1851. 
The experiments on diffusion to be presently described are in continuation of those 
detailed in my last publication on the subject, the same method of observing being 
followed without change. The diflpusion is generally made from solutions in four 
different proportions, so as to exhibit pretty fully the characters of the property in 
question for each salt, so far as is possible at a constant temperature. The salts 
operated upon are of two bases only, potash and soda; but the acids are consider- 
ably varied, so as to include hydrates, carbonates, sulphates, sulphites, hyposulphites, 
sulphovinates, oxalates, acetates and tartrates. Salts of almost every class of acids 
come thus to be represented, either in the present or former series of experiments on 
diffusion, while at the same time much information is elicited respecting the diffusive 
relation of the two important bases named. 
Comparison of Salts of Potash and Soda. 
Hydrate of Potash. — Time of diffusion 4'041 days. The usual number of eight 
cells of the 1 and 2 per cent, solutions of this substance were diffused, and four cells 
of the 4 and 8 per cent, solutions. The whole diffusates of each proportion were then 
mixed together, and the quantity of hydrate of potash diffused for two cells deter- 
mined by an alkali metric experiment, which was always repeated twice. 
1. One per cent, of hydrate of potash, density T00978, diffused at 63°'43 gave 6-56 
grs. of hydrate of potash for two cells. 
2. 2‘005 per cent, of hydrate of potash, density T01878, diffused at 63°'4, gave 
12’88 grs. for two cells ; calculated for 2 per cent., ]2‘84 grs. of hydrate of potash in 
two cells. 
3. 4‘01 per cent, of hydrate of potash, density T0366, diffused at 63°'4, gave 12'56 
grs. for one cell; calculated for 4 per cent., 12'52 grs. of hydrate of potash in one 
cell. 
4. 8’02 per cent, of hydrate of potash, density T07069, diffused at 63°‘4, gave 
26'20 grs. for one cell; calculated for 8 per cent., 26T2 grs. of hydrate of potash in 
one cell. 
