TUANSACTIONS OF SECTION B, 597 



The two latter samples were the tiuest. It is evident that there is some 

 impurit}' contained in these samples, which were quite free Irom potash when a 

 quantity of 5 grams was reduced, extracted with water, and tested spectroscopically. 



To check these results two samples of black oxide of manganese, obtained by 

 heating the nitrate, were reduced in hydrogen to manganous oxide, and the water 

 collected. These gave for manganese the atomic weights of 53-6 and 53-3 respec- 

 tively. These are the results of preliminary experiments ; others are being carried 

 out with purer samples and greater accuracy. 



WI:B^'ESI)AY, SEPTEMBER 7. 

 The following Papers were read : — 



1. On Some Vajpour Deiisity Determinations. By Professor Dewae, M.A., 



F.B.S., and A. Scott, B.A., B.Sc. 



It seemed to the authors that the behaviour" of various haloid salts at high tem- 

 peratures would prove of great interest on account of its relation to the experiments 

 of Meyer and Crafts on the vapour density of chlorine at high temperatures. The 

 method they employed was to measiu'e the volume of gas given off from a weighed 

 amount of substance which was introduced in the ordinary way into an iron 

 apparatus in every respect the same as they used in determinhig the vapour- 

 densities of potassium and sodium, which is described in the ' Proc. Roy. Soc' 

 The residts of the experiments are calculated so as to give the amount of substance 

 required to expel 22-4: C. of gas at 0° + 760 mm. pressure. Commencing with iodine 

 they found that in an apparatus filled with hydrogen the mean result was 260, I^ 

 being equal to 254 ; when nitrogen was used, 241 was the number found. 



Platinous chloride gave in the same way the number 251, 268 corresponding to 

 Clj. No free chlorine could be detected ; ferrous chloride was apparently formed 

 alone. Ferrous chloride was next tried and gave as a mean 116 : — 



FeCl2 = 127. 



No absorption-spectrum could be seen, but a small quantity of free chlorine 

 seemed to exist in the vapour, the rest being Fed.,. Manganous chloride gave 135 

 while MnC1.3 = 126. Argentic chloride when introduced seemed to volatilise at 

 once, and on calculating gave 262 as a mean instead of 287. It, however, was 

 almost entirely decomposed into ferrous chloride and silver, as on blowing out the 

 vapour only a minute trace of silver could be found. 



With argentic iodide they got the number 428 if the iodide was first fused in 

 the small capsule before being introduced into the apparatus ; otherwise they got 

 the muuber 574, Ag^I^ corresponding to 470. In the vapour there were silver and 

 ferrous iodides along with free iodine ; lead chloride gave. 239, whereas PbCl, corre- 

 sponds to 278. On looking down the tube with the spectroscope a beautiful chan- 

 nelled spectrum was observed. Potassium chloride was tried, but they were never 

 able to raise the temperature sufficiently to volatilise this salt rapidly enough to 

 get good results. Potassic iodide gave as a mean 183 instead of 166. The vapours 

 blown out seemed to contain neither iodine nor iron, but yielded a fine white powder 

 of potassic iodide which had a slight acid reaction. Eubidium chloride similarly 

 gave 155 instead of 121. 



2. OnVa;poi(,r Density Beterminatioiis. 5?/ Professor Thorpe, P/t.D., F.B.S. 



3. Note on the Phosphates of Lime and Ammonia. By J. Alfued Wanklyn. 



When ammonia is added to a solution of the soluble phosphate of lime, a 

 precipitate of tribasic phosphate of lime is thrown down, and phosphate of ammonia 

 passes into solution. 



