Dr. E. J. Mills on Elective Attraction. 511 



Plumbic Nitrate. 



A specimen of plumbic nitrate obtained by three crystalliza- 

 tions of a commercial sample (the mother-liquor being rejected 

 at each operation) was found to be sufficiently pure. By evapo- 

 ration with hydric sulphate it appeared to contain 62*61 per cent, 

 lead, theory requiring 62*55 per cent. On account of the tena- 

 city with which this salt retains a small percentage of water, 

 even at 100°, it was powdered finely and heated in an air-bath 

 to 180°-185° during an interval varying from eighteen to forty- 

 two hours. The reaction-tube generally received its supply of 

 nitrate at the latter temperature, after which it was closed im- 

 mediately and cooled. 



On bringing the oxychloride and nitrate together, some slight 

 commencement of action was usually perceptible in the cold. 

 At 60° the liquid became turbid and acquired an orange colour ; 

 at 82° a gas was evolved closely resembling chlorine in smell 

 and appearance, but of too light a colour to contain much nitric 

 peroxide. At 100°, however, the tint of the gas had become a 

 deep orange; and at 115° some phosphoric oxychloride emerged 

 from the apparatus, having hitherto been retained, doubtless, by 

 the nitrate, just as water ia retained, above its point of ebullition. 

 Hence it was necessary to heat the residue to a higher degree 

 than was required in the case of the silver-salt — an operation 

 which, it was found, could be carried out with safety below 162°. 

 Above this temperature a secondary and different reaction is 

 speedily accomplished. The average time employed in one ex- 

 periment was about If hour. The residue had a faint yellow 

 tint, and did not, for the most part, become heated in contact 

 wdth cold water. But it was several times observed that, w^hen 

 the water reached the exit end of the body of the reaction-tube, 

 considerable heat was produced — an evident indication that the 

 pho.sphoric oxide had wholly, or almost wholly, collected in that 

 spot. 



For analysis, the contents of the tube were transferred to a 

 beaker, and heated for twelve hours with aqueous and hydric 

 nitrate. The argentic chloride so formed was weighed in the 

 usual manner, and calculated as plumbic chloride; the filtrate 

 from it, after addition of ammonia until a precipitate began to 

 form, was treated with ammonic hydrosulphide; and after pro- 

 longed repose, the final filtrate was precipitated with magnesia 

 mixture. 



The experiments exhibit a varying discrepancy, owing, as is 

 probable, to the action of that portion of the oxychloride which 

 was expelled at 1 15°, and which, being no longer in excess of the 



