Chemical Constitution of Saline Solutions. 



263 



Comjmsition of a second Hijdrate. 



Some of the hydrated crystalline salt was placed in a watch-glass over sulphu- 

 ric acid under a bell-jar, and weighed at intervals during a fortnight until the 

 weights became practically constant. The temperature varied from about 1 F C. to 

 16^ C. during this period. The colour of this salt is yellow. 



"Weight of salt taken, 2-1845 



Loss of weight = H,0, 0-4931 



HjO lost, per cent. 22-58 



II. 

 5-5618 

 1-2398 

 22-29 



We arrive then at the following figures as expressing the hydration of the salt 

 dried at the normal temperature when kept in a dry atmosphere. 



I. II. 



Per cent. Per cent. 



Water lost by crystals at 100° C, 33-47 32-21 



Water lost over sulphuric acid, 22-58 22-29 



Combined water in hydrate, 10-89 10-92 



This is one-third that in the original salt which, as will be seen below, is six 

 molecules. 



Foimd. 



Composition of the ttvo Hydrates. 



Calculated for NiBra-GHjO. 



I. 



Ni, 18-83 



Br, — 



H.O at 20° C, . . . 33-47 



II. 

 17-92 

 48-61 

 33-21 



99-74 



Composition deduced from the Analysis. 



Ni, 2i-\^ per cent. 



Br, 62-75 „ ,, 



H,0, 14-07 ,, „ 



100 00 



17-96 j»«/- cent. 

 48-97 „ ,, 

 33-07 ,, ,, 



100 00 



Calculated for NiBrySH-jO 

 23-17 per cent. 

 62-72 „ ,, 

 14-11 ,, „ 



100-00 



Nickel Iodide and its Hijdrates. 



As in the previous case, nickel clippings to the amount of 59 grs. were placed 

 in a platinum dish and covered with iodine and water. As the action was slow 

 some hydriodic acid was prepared specially for the purpose and added to the 

 contents of the dish. As soon as hydrogen was evolved, more iodine was added 

 until all the metal had entered into solution. Excess of iodine was removed by 

 boiling. 



The solution wliile hot and concentrated was of a rich brown colour, but on 

 cooling it became moss-green. The hydrated salt crystallized out in handsome 



20 2 



