1900.] P. 0. Ray — Mercurous Nitrite and its Derivatives. 487 



hot mother liquor also bright scarlet spangles of mercuric iodide 

 crystalline out on cooling. 



Result of Analysis : — Estimation of iodine. The methods des- 

 cribed in the standard works of Presenilis, Crookes, &c, for the estima- 

 tion of iodine in mercurous iodide appeared to be tedious and trouble- 

 some in view of the numerous determinations involved. Reduction was 

 effected with zinc and sulphuric acid under certain modifications. The 

 compound is finely powdered and transferred to a flask. Pure granu- 

 lated zinc and dilute sulphuric acid are then added together with a 

 few pieces of scrap platinum, when evolution of hydrogen at once sets 

 up ; the flask is kept actively rotated. After a few minutes the zinc 

 becomes amalgamated and further action ceases. A drop of platinic 

 chloride is now added, reduction proceeds, aud a pink colour pervades 

 the liquid, and the flask is shaken as before. When the reduction is 

 complete the solution should be perfectly clear and colourless, and there 

 should not be any trace of a powdery black residue at the bottom of 

 the flask. The iodine is estimated in the usual way, and the additional 

 halogen introduced with the standard Pt.Cl 4 drop, corresponding in the 

 present instances to 0-005 AgCl, allowed for. Sometimes the zinc is 

 treated beforehand with the dilute acid and a few drops of PtCl 4 , and 

 the platinized zinc, washed free from chlorine, is added in successive 

 instalments to bring about reduction, which is finished in 20 miu. to 

 half an hour. 



As control experiments, iodine in resublimed mercuric iodide was 

 estimated according to the above method. Thus : 



(1) 0-2232 g. gave 2324 Agl 



(2) 0-0604 „ „ 0625 „ 

 Calc. for Hgl 2 Found 



I: 5595 I II 



56-27 5600 



Result of analyses of the dark brown, orange-yellow and yellow modi- 

 fications of mercurous iodide. 



(1) 0-4282 g. gave 03043 Agl whence 1 = 38-40 



(2) 02204 „ „ 01577 „ „ ,, = 38-67 



(3) 0-2558 „ „ 01834 „ „ ,, = 38-74 



(4) 2038 „ „ 0-1446 „ „ „ = 38*34 



(5) 0-0824 „ „ 0-0587 „ „ ,, = 38-47 



Theory for Hgl requires 1 = 38 84 °/ oi the Mercury amounted to 

 6124 %> tna ^ demanded by theory being 61*16 °/ . 



