of Expansion of Gas* Solutions* 

 Table IV. 



119 



No. 



Percentage 

 of NH 2 . 



Saturation. 



Maximum 

 density. 



i 

 Freezing. 



1 



29-00 per cent. 

 16-19" „ 



7-96 



5-61 



2-12 



000 (water) 



39-80 * 

 59-00 

 76-40 

 83-10 

 93-20 

 100-00 



-10-50 

 - 7-20 

 + 0-80 

 -1- 4-00 



-14-10 

 -10-60 

 - 5-40 (?) 

 0-00 



2 



3 



4 



5 



6 





We thus find that in the case of aqueous solutions of ammonia 

 the freezing-point and point of maximum density are lowered 

 by the presence of the gas in solution f . Before the law of 

 this change can be given, many more experiments, covering a 

 much greater range of temperature, will have to be made. 

 The only attempts to freeze aqueous ammonia, of which we 

 have found record, are those of Fourcroy and Yauquelin in 

 1797$. 



Their statement, which still finds place in our chemical text- 

 books and dictionaries, is that a well-saturated solution (bien 

 saturde) freezes at —40° C. Since the freezing-point is a 

 rapidly changing function of the amount of gas in the solu- 

 tion, this statement is of little use without a knowledge of the 

 strength of the solution in question. An examination of the 

 curves in fig. 2 leads us to suspect that the solution frozen by 

 Fourcroy and Yauquelin was the ordinary commercial solu- 

 tion of about 16-per-cent. strength. 



Just as the determination of the freezing-point had, up to 

 the time of the present work, been confined to observations 

 upon a single solution, so with the study of the coefficients of 

 expansion; we find but a single research on this subject 

 (by Prof. Munke of Heidelberg, in 1828§). His observations, 

 which extended to a variety of liquids, were made with the 

 greatest care and exactitude; his study of aqueous ammonia, 

 however, was confined to a single solution; so that no general 

 conclusions concerning the influence of the strength of a solu- 

 tion upon its behaviour could be drawn. 



* Roscoe and Dittmar, l Quarterly Journal of the Chemical Society.' 



t A similar lowering of the point of maximum density due to the pre- 

 sence of C0 2 gas in water has been noted by Mackenzie and Nichols in 

 their paper " Ueher die Volumenvermehnmg von Fliissigkeiten durch 

 die Absorption vonGasen," PoggendorfFs Annalen, n. F. iii. 1878. 



X Fourcroy and Vauquelin, Annates de Chimie et de Physique, s£r. 1, 

 t, xxix. 



§ Munke, St, -Petersburg Academy, M&moirespar divers Savants, 1831. 



