TRANSACTIONS OF SECTION B. 509 



3. On the Action of Heat on the Selenate of Ammonium * By Dr. Edmund 

 W. Davy, Professor of Forensic Medicine, Boyal College of Surgeons, 

 Ireland. 



The author read on behalf of his colleague Dr. Charles A. Cameron and 

 himself a paper containing the results of some observations which they had con- 

 jointly made on the action of heat upon the selenate of ammonium. The study 

 of the effects of that agent on the sulphate of ammonium, having in the hands of 

 different chemists led to interesting results, the authors thought it desirable to insti- 

 tute some experiments on the selenate of that base, to ascertain whether any corre- 

 sponding products would be obtained by its exposure to heat, selenic and sulphuric 

 acids agreeing so closely in their properties, and this subject being hitherto unin- 

 vestigated as far as they were aware. 



Some selenate of ammonium, after thorough drying at 100° C, was heated in a 

 bath of paraffine, the degrees of temperature to which it was exposed bein°- indi- 

 cated by a thermometer. It was found that when the salt was heated to° about 

 180° C.,_the evolution of a minute quantity of ammonia could be readily detected, 

 and finding that the amount evolved increased with the rise of temperature the 

 heat was gradually raised to about 250° C, when the development of ammonia be- 

 came much more abundant, whilst at the same time water and selenium be^an to 

 be separated. ° • 



_ This temperature was then continued as long as ammonia was evolved, and till 

 acid vapours made their appearance, when the heat was withdrawn. 



On examining the residue after this treatment, it was found that the selenate of 

 ammonium had been completely decomposed, selenium and selenious anhydride 

 being the remaining products. Wishing to ascertain if any gaseous matter was 

 evolved during the decomposition, some selenate of ammonium was heated in a tube 

 filled with mercury, when a considerable volume of a gas not absorbed by water 

 was obtained, which on examination was found to be nitrogen. It should also be 

 stated, that the salt was observed to have acquired a strong acid reaction, before its 

 final breaking up at the highest temperature to whicb it had been exposed in the 

 paraffine bath ; indicating the formation of an acid salt in the first sta°-e of its de- 

 composition by heat. From the results of those and of other experiments made by 

 the authors, they have come to the conclusion, that when selenate of ammonium is 

 heated it first resolves itself into ammonia and an acid selenate of ammonium and 

 that this salt, on further heating, breaks up into selenium, selenious anhydride water 

 and nitrogen, and that the reactions which occur in the process may probablv be 

 expressed by the following formulas : 



1st stage.-4[(NH 4 )*Se0 4 ] = 4(NH 4 . H. Se0 4 ) + 4NH 3 . 



2nd stage.— 4(NH 4 . H. Se0 4 ) = Se + 3Se0. 2 + 10(H 2 O) + N 4 . 

 A number of circumstances, however, have as yet prevented the authors beino' able 

 to confirm the correctness of the above formula? by actual results. 



In conclusion, the foregoing observations are interesting, as they show that in the 

 first stage of the decomposition of the eelenate of ammonium by heat there is an 

 acid salt formed, like as in the case of the sulphate, of that base when similarly 

 treated, as was pointed out by Dr. Schweitzer ; but in the separation of selenium, in 

 the second stage of the process, there is no analogy in the case of the sulphate of 



nnimnnnim * 



ammonium. 



4. A New Method of Alkalimetry. By Louis Siebold, F.C.S. 



The method recommended by the author consists in the reverse application oi 

 Liebigs process for estimating hydrocyanic acid, and is based on the fact that the 

 volumetric determination of an alkaline cyanide by means of silver nitrate is in no- 

 wise affected by the presence of free hydrocyanic acid. From the volume of silver 

 solution used, the quantity of alkali may be as readily calculated as that of the 

 cyanogen. If the applicability of this process for alkalimetric purposes were con- 

 * In extenso in the « Chemical News,' Vol. XXXVIII. 133. 



