TS EELATION TO CHEMICAL COMPOSITION. 
379 
Table VI. — ^Transpiration of Formic Acid, at 20°, by Capillary C shortened. 
(Transpiration-time of water, 293 seconds.) 
Water added to 100 acid 
Water, per cent. 
Transpiration-time. 
Specific graTitv, 
at 15^ 
In seconds. 
Water =1. 
3-73 
3-6 
503-5 
1-718 
1-2265 
19-56 . 
. 1 eq. 
16-35 
484-5 
1-653 
1-2019 
39-13 . 
. 2 eqs. 
20-93 
435-5 
1-486 
1-1765 
58-69 . 
. 3 eqs. 
36-98 
411 
1-402 
1-1524 
68-47 . 
. 3*5 eqs. 
40-64 
401-5 
1-368 
1-1466 
78-26 . 
. 4 eqs. 
43-90 
402-5 
1-372 
1-1408 
97-82 . 
. 5 eqs. 
49-44 
388-5 
1-325 
1-1275 
1 1 7-35 . 
. 6 eqs. 
53-99 
376-5 
1-284 
1-1203 
136-95 . 
. 7 eqs. 
57-79 
359 
1-225 
1-1062 
Hydj'ocMoi'ic Acid. 
The most concentrated form of this acid that was dealt with, acid of sp. gr. 
1T553, contained already upwards of 8 equivalents of water. Its transpiration- 
time was 1‘7356, referred to the time of water as I. With further dilution the time 
diminished, till at the proportion of 12 equivalents of water the time had fallen to 
1’5287. About this point the rate of diminution is reduced, and the transpiration-time 
even becomes stationary for a short portion of the range of hydration. The retardation 
observed appears to coincide with the formation of a 12-hydrate of hydrochloric acid. 
The existence of such a compound is further supported by the fact that solutions of 
hydrochloric acid tend to the same composition by evaporation at the atmospheric tem- 
perature. The degree of hydration of most stability at high temperatures, and having 
the highest boiling-point, is known to be at or near the proportion of the 16-hydrate. 
The existence, however, of the latter hydrate, at the ordinary temperature, is not sup- 
ported by the transpiration experiments now recorded, conducted as these were at a low 
temperature. 
Table VII. — Transpiration of Hydrochloric Acid, at 20°, by Capillary C. 
(Transpiration-time of water, 348 seconds.) 
Water added to 100 acid 
(HCl). 
Water, per cent. 
Transpiration-time. 
Specific gravity, 
at 15°. 
In seconds. 
Water =1. 
221-8 
69-23 
604 
1-7356 
1-1553 
250 
71-42 
569 
1-6336 
1-141 1 
280 
73-67 
536 
1-5404 
1-1303 
290 
74-36 
5.32 
1-5287 
295-89 ... 12 eqs. HO 
74-74 
532 
1-5287 
1-1246 
300 
75-00 
520 
1-4942 
310 
75-60 
516 
1-4827 
1-1202 
.380 
79-20 
486 
1-3965 
1-1021 
394 ... 16 eqs. HO 
79-97 
479 
1-3764 
1-0992 
410 
80-39 
469 
1-3476 
1-0961 
3 G 
JIDCCCLXI. 
