228 
Proceedings of the Poyal Society of Edinburgh. [Sess. 
Preparation. — Different proportions of silver nitrate and methylene 
iodide yielded the same product, although with excess of methylene 
iodide in bulk a solid yellowish substance or mixture was also formed 
which was not further examined. It was converted into the colour- 
less double compound on the addition of alcoholic silver nitrate solu- 
tion. With a decinormal solution of silver nitrate the yield of 
AgN 03 .CH 2 l 2 was, with molecular quantities, 75 per cent, of the 
theoretical ; with two molecular quantities of silver nitrate it was 90 per 
cent., and with two molecular quantities of methylene iodide 100 per cent, 
of the theoretical. 
To obtain the compound in a pure form it is necessary to use an 
alcoholic solution of silver nitrate not less than decinormal in strength. 
With a fortieth normal solution none of the compound is precipitated, but 
the solution becomes opalescent owing to the formation of silver iodide. 
With a twentieth normal solution crystals of the double compound begin 
to be deposited in about two minutes, but they increase in number rela- 
tively slowly, and a small quantity of silver iodide is soon formed, so that 
the product is liable to become impure. Some silver iodide is eventually 
formed when saturated solutions of silver nitrate are employed, but the 
stronger the silver nitrate the later it is in appearing. The substance is 
most conveniently prepared by adding pure methylene iodide to a saturated 
solution of silver nitrate in alcohol, filtering in two or three minutes^ 
washing the crystals rapidly with absolute alcohol followed by anhydrous 
ether, pressing between filter paper and drying in an incubator at 38° C. 
So prepared the product retains a small amount of alcohol, which com- 
bustion shows to be about 4 per cent, of the weight of the compound. The 
alcohol is dissipated by placing the substance in an evacuated desiccator 
left in the dark for three days. Longer retention is inadvisable owing to 
the gradual evolution of CH^Ig. 
The following analytical results were obtained : — 
0'2845 gm. gave 0*0285 gm. CO .2 and 0’0152 gm. H 2 O. C= 2*73. H = 0*59. 
0*4173 gm. „ 11-8C.C. Isk ^ N=3*50. 
2*3079 gms. ,, 0*570 gm. Ag. Ag = 24*7. 
8*5629 gms. ,, 4*914 gms. I. 1 = 57*4. 
AgN 03 .CH 2 l 2 requires 0 = 2*74; H = 0*46; N = 3*20; Ag = 24*7; 1 = 57*7. 
The substance is moderately soluble in absolute ethyl alcohol — 100 gms. 
dissolve 1*7 gms. at room temperature (16°-18° C.) — but it gradually 
undergoes decomposition in it and cannot be recrystallised from it. 
Of the solvents we have tried for recrystallisation absolute methyl 
