On Salt- Solutions and Attached Water. 105 



I made observations with the 32 fork, the pitch of which 

 was marked on it by the maker, of the value of c required 

 to produce a balance, then doubled this value of c, and set the 

 fork which it was required to adjust to drive the commutator. 

 Leaden weights were then fixed with screws on to the prongs 

 of the fork, and their position was adjusted until the galvano- 

 meter-balance was not disturbed on making contact. It was 

 clear, then, from the approximate formula that the frequency 

 of the fork was very nearly 16. And on making the comparison 

 with the clock, it was found to be 15*866, as already stated. 



My thanks are due to Messrs. Wilberforce, Whitehead, and 

 Fitzpatrick for assistance in making the experiments. 



XII. On Salt-Solutions and Attached Water, — VIII. 

 By Frederick Guthrie. 



[Concluded from p. 35.] 



§ 242. nriHERMAL Relation of some Aniline Salts to Water. — 

 In turning to organic ammonias and their salts 

 which contain radicals of greater molecular weight, and belong- 

 ing to different series from those we have been considering 

 above, we are tempted by aniline. It can be got in a state 

 of great purity. Its salts are well defined and stable, and of 

 various degrees of solubility. The aniline I employed was 

 rectified several times, converted into the chloride, and twice 

 recrystallized; reconverted into the base by caustic potash, 

 dried, and finally distilled. 



Aniline is slightly soluble in water. On cooling to a tem- 

 perature of — 0°*7, the water and aniline solidify together as 

 a porcelain-like opaque cryohydrate, which is, however, too 

 poor in aniline to be capable of satisfactory analysis. 



§ 243. Chloride of Aniline. — As a cryogen, the chloride of 

 aniline gave a temperature of — 10 o, 5. For its solubility the 

 weighed solution was evaporated in a water-bath until it 

 ceased to lose weight. Saturated at 13° # 1, it was found that 

 8*3210 grams gave 3*8875 anhydrous salt, or 46*72 per cent. 

 Saturated at 0°, 13*2836 grams gave 5*3595 grams dry salt, or 

 40*35 per cent. The solution saturated at 0°, or a 20-per-cent. 

 solution placed in a freezing-mixture, falls to the temperature of 

 — 10°*7. It is here as generally preferable to reach the cryo- 

 hydrate from the dilute side. This cryohydrate readily forms a 

 supersaturated solution. Of the cryohydrate, 7*1760 grams 

 gave 2*2860 dry salt, or 31*86 per cent. 



Percentage solutions were then made, and their temperatures 

 of initial solidification determined. 



