876 
ME. T. GBAHAM ON LIQUID TEANSPIEATION 
SulpTiuric Acid. 
Table II. — Transpiration of Sulphuric Acid, at 20°, by Capillary G. 
(Transpiration-time of water, 109 seconds.) 
Water added to 100 acid 
(SHO,). 
Water, 
per cent. 
Transpir 
In seconds. 
ation-time. 
Water =1. 
SpeclSe gravity, 
at 15°. 
0 
0 
2360 
21-6514 
1-8456 
2-5 
2-43 
2412 
22-1284 
1-8398 
5 
4-76 
2451 
22-4862 
1-8346 
10 
9*09 
2516 
23-0825 
1-8120 
12-5 
11-11 
2548 
23-3761 
1-7976 
15 
13-04 
2587 
23-7340 
1-7800 
17-5 
14-89 
2591 
23-7706 
18-36 ... 1 eq. HO 
15-13 
2466 
22-6238 
1-7590 
20 
16-66 
2398 
22-0000 
1-7473 
30 
23-07 
1523 
13-9724 
1-6700 
36-73 ... 2 eqs. HO 
26-86 
1189 
10-9090 
1-6335 
40 
28-50 
1056 
9-6880 
1-6146 
50 
33-33 
810 
7-4302 
1-5600 
60 
37-50 
626 
5-7431 
1-5118 
70 
41-17 
535 
4-9082 
80 
44-44 
450 
4-1284 
100 
50-00 
382 
3-5045 
120 
54-54 
332 
3-0458 
140 
58-33 
290 
2-6605 
160 
61-53 
260 
2-3889 
180 
64-28 
241 
2-2110 
200 
66-66 
227 
2-0825 
The transpiration of sulphuric acid is very slow, being twenty-four times less rapid 
than that of water, as might be expected from the viscous quality of the acid fluid. It 
is surprising, however, that the first additions of water do not promote the transpira- 
tion, although they lessen in a sensible degree the viscosity of the liquid. The tran- 
spiration-time increases from 2360 to 2591 seconds, and then attains the maximum, when 
17’5 parts of water have been added to 100 parts of oil of vitriol. The proportion of 
water named approaches closely to 1 equivalent (18‘36 parts). Indeed it is quite pos- 
sible that the acid mixture which exhibits the least transpirability might have contained 
a full equivalent of water, for a portion of aqueous vapour may have been absorbed horn 
the air during the process of filling the bulb. That the crystallizable hydrate of 
sulphuric acid, SH04-1-HO, is the liquid of least transpirability is, I believe, the proper 
inference from these observations. With increasing proportions of water the transpira- 
tion-time rapidly diminishes, till the time is reduced to 227 seconds in a mixture of oil 
of vitriol with twice its weight of water. 
A more minute examination than has been attempted would be required to show 
whether the existence of other definite hydrates |[of sulphuric acid may be indicated by 
a perceptible retardation in the time of transpiration. 
