378 
im. T. aEAHAM ON LIQUID TEANSPIEATION 
acetic acid, but the time rises to 3-341 with 3 equivalents of water. With 3*8 equiva- 
lents of water the time is 2-975, and has accordingly very sensibly receded, the maxi- 
mum point bemg passed. It is conceivable that the relation to acetic acid is slightly 
modified m butyric acid by the interference of some other physical property, such as 
unctuosity, that is unequally developed in the two acids. 
ValerianiG Acid. 
The hydration of this acid cannot be carried beyond 2 equivalents, but up to that 
point the transpiration is retarded by every addition of water, as in acetic and butyric 
acids. "While the basic hydrate (CjoHiq 04 ) is transpired in 2-155 times the water 
period, the time increases to 3-634 with 1 equivalent of water added, and to 3-839 with 
2 equivalents. 
Table — Transpiration of "Ualerianic Acid, at 20° C., by Capillary C shortened. 
(Transpiration-time of water, 290 seconds.) 
Water added to 100 acid 
(C^io ^10 
Water per cent. 
Transpiration-time. 
Specific gravitr, 
at 15°. 
In seconds. 
Water =1. 
0 
0 
625-2 
2-155 
•9350 
8-82 ... 1 eq. HO 
8-10 
1054 
3-634 
-9484 
17*64 ... 2 eqs. HO 
15-84 
1113-5 
3-839 
-9519 
Formic Add. 
Formic acid appears to diverge considerably from the other members of the acetic 
acid series in certain physical and chemical characters. "While the acetic hydrate is 
lighter than water, and is increased in density by the addition of water, the formic 
hydi-ate has a higher density than water, and has its density uniformly lowered by dilu- 
tion, as will be seen in the Table which follows. The transpiration-time of formic acid 
is also highest in a concentrated state, and diminishes with dilution in the same regular 
manner as the density, shovring no evidence of the acetic maximum at the point of 
2 equivalents of water. Indeed, formic acid does not appear to affect that particular 
degree of hydi-ation so characteristic of the acetic acid series. Hence it is, also, that we 
have no subformiate of lead corresponding with the subacetate of lead, and have occa- 
sion to remark a general absence of basic formiates. The physical properties of hquid 
formic acid are more suggestive of hydrochloric acid than they are of acetic acid. 
The most concentrated formic acid that could be prepared still contained 3-6 per cent, 
of water. The transpiration-time of that liquid, it will be seen, is 1*718 refen-ed to 
water as 1 ; and of the 2-hydrate 1*486. There is evidence of retardation between the 
points of 3 and 4 equivalents of water, but it is difiicult to say with which of 
these two hydrates the retardation should be connected. More numerous and minute 
observations would be required to settle the point. We can only draw the negative 
conclusion from the Table, that the maximum retardation does not coincide with the 
2-hydrate as in acetic acid. 
