OF ARTS AND SCIENCES. 211 



paper is a very different phenomenon from the retention of undecom- 

 posed oxides of nitrogen alluded to by Marignac,* Morse and Burton, 

 and others. Nitrogen present in the stcate of gas could of course give 

 no test with sulphauilic acid and naphthylamine, or any other test for 

 oxidized nitrogen. It is evident that the phenomenon we are now 

 studying, like the other just spoken of, may be a very serious cause 

 of error in many of the published determinations of atomic weights ; 

 these would hence appear lower than their true value, because of the 

 extra material which is calculated a% oxygen.f Before any quantita- 

 tive results obtained in this way can be accepted as authoritative, 

 definite proof must be brought forward of the absence of this source 

 ot error. It is to be hoped that the able experimenters who have 

 recently worked upon zinc, nickel, magnesium, and similar metals, 

 have preserved typical specimens of their final products. If this is 

 the case, nothing could be easier than to determine the amount of 

 occluded gas, if any is present, and to apply the necessary correction. 

 As long ago as 1887 one of us was engaged, through the suggestion 

 of Professor Cooke, upon an investigation of the atomic weight of zinc 

 depending upon the analysis of zincic bromide. The work was dis- 

 continued because of the many publications upon this subject which 

 appeared before it could be completed. Since the results recorded in 

 this paper appear to indicate that the last word has not yet been said 

 upon the subject, the investigation of zincic bromide and chloride is 

 now being continued in this Laboratory. 



* " II est probable que I'oxyde de zinc et la magnesie ne sont pas les seuls 

 oxydes qui retiennent aussi e'nergiqueiiient des composes nitreux, lorsqu'on les 

 prepare par la calcination de leurs azotatcs." — Aniiales de Chemie et de Phy- 

 sique, Series [6], Vol. I. p. 311, foot-note. 



t The following are the metals whose atomic weights have been determined 

 by means of the o.xide made through action of nitric acid : Hydrogen (cupric 

 oxide), Magnesium, Aluminium, Vanadium, Manganese, Nickel, Cobalt, Copper, 

 Zinc, Gallium, Selenium, Tin, Antimony, Tellurium. See Meyer and Seubert, 

 Atomgewichte, pp. 17 to 42. Also Nickel, Kriiss, Z. anorg. Chem., II. 235. Zinc, 

 Morse and Burton, Amer. Chem. Journ., X. 311-321. Magnesium, Burton and 

 Vorse, Chem. News, LXII. 267. 



