820 
Proceedings of the Royal Society 
the solution, calculated from the number l , 53 = sp. gr. solid am- 
monium chloride, being given in the right-hand column. 
Table I. 
Observer. 
Per cent. 
Observed sp. gr. 
Theor. sp. gr. 
Hassenfratz,* * * § . 
19-3 
1-0693 
1-0718 
Michel et Krafft, t . 
247 
1-0752 
1-0935 
Schiff, J . 
26-9 
1-0767 
1-1028 
Gerlach, § 
26*3 
1-0766 
1-1002 
Schiff (loc. cit.) says, that the fact already observed by Michel 
and Krafft — that ammonium chloride expands on dissolving in 
water is confirmed by his experiments, but is unable to offer any 
explanation of the cause of it. While Gerlach, writing in 1859, 
and again in 1 862, || after a long series of most careful experiments, 
extending over numerous salt solutions of various strengths, and 
with complete knowledge of the work done on the subject by 
Kremers, Schiff, Karsten, and others, has no hesitation in stating, 
that in the act of solution contraction takes place in the case of all 
anhydrous salts, with the single exception of ammonium chloride. 
Finally, Sorby (loc. cit.) found that, in the case of salts which pro- 
duce contraction on solution in water, the effect of pressure is to 
increase the solubility, while with ammonium chloride the reverse is 
the case ; pressure, as was to be expected, diminishing the solubility. 
Not only is the specific gravity of solutions of Ammonium 
chloride abnormal, as shown above, but some of the other proper- 
ties of the solution also show a variation from those to be expected 
from a consideration of the properties of solutions of potassium and 
sodium chlorides. For example, Quincke IF has determined the 
cohesion or surface tension of solutions of ten chlorides, including 
ammonium chloride, by means of the method with capillary tubes 
and that with air bubbles. On comparing the results of experiment 
* Annales de Chimie, xxviii. 298. 
t Ann. de Chim. et Phys. [3], xli. 471. 
X Annalen der Chemie , cix. 330. 
§ Spec. Gen. der Salzlosungen. Freiberg , 1859, p. 11. 
|| Zeitschrift fur Analyt. Chem., viii. 271. 
IF Pogg., Annalen , clx. p. 560, 
