CHEMISTRY — JONES. 185 



as in the case of silver phosphate, the dried salt contained a slight residue 

 insoluble in dilute nitric acid. Preliminary determinations have shown, 

 however, that the composition of this insoluble residue is very close to that 

 of tri-silver arsenate, so that no appreciable correction is involved. At the 

 present stage of the investigation no certain results can be given. 



As a check upon the value 54.96 (Ag= 107.93) ^o^ the atomic weight of 

 manganese, found by Dr. M. A. Hines (see Jour. Amer. Chem. Soc, vol. 28, 

 p. 1560, 1906), Mr. Hobart H. Willard attempted the analysis of silver 

 permanganate. This salt, even when very pure, proved entirely unsuited for 

 accurate work, on account of the ease with which it is decomposed. In the 

 hope that the loss of oxygen could be brought to a constant point by ignition 

 in an atmosphere of hydrogen, with the formation of the mixture of metallic 

 silver and manganous oxide which may be represented by the formula 

 Ag.MnO, many reductions of this sort were carried out. Then the silver 

 content of the residues was determined, after solution in nitric acid. These 

 preliminary experiments, which consumed much time and energy, showed 

 that neither platinum nor quartz could be used as a containing vessel, since 

 at temperatures high enough to insure complete reduction, the former alloys 

 with the silver and the latter is attacked by the oxide. As a last resort boats 

 of metallic copper were employed, the boats being dissolved in nitric acid at 

 the same time as the residue. This method gives indications of success. 



With Mr, John H. Wilson the atomic weight of lead was investigated by 

 the analysis of lead chloride. Very pure specimens of this salt were pre- 

 pared for analysis by fusion in a current of dry hydrochloric acid gas. Then, 

 after solution in water, the chloride was titrated against a weighed equiva- 

 lent amount of the purest silver. Finally the precipitate of silver chloride 

 was collected and weighed. From both ratios, PbCl, : 2Ag and PbCls: 2 

 AgCl, the atomic weight of lead is found to be 207.19 if the atomic weight 

 of silver is assumed to be 107.930. With silver at 107.88, the atomic weight 

 of lead becomes 207.09. This result is nearly two-tenths of a unit higher 

 than the generally accepted value. 



Jones, Harry C, Johns Hopkins University, Baltimore, Maryland. Grant 

 No. 387. Continuation of investigations on absorption spectra of certain 

 salts in aqueous and non-aqueous solvents. (For previous reports see 

 Year Book No. 2, p. xxx ; Year Book No. 3, p. 106 ; Year Book No. 4, 

 pp. 151, 152, and Year Book No- 5, pp. 149, 150.) $1,000. 



The problem of hydration in aqueous solution has been studied during 

 the past year from three different standpoints : 



(i) The relation between the dissociation of electrolytes as measured 

 by the freezing-point, and by the conductivity methods. 



(2) The effect of one salt, with a given hydrating power, on the hydrating 

 power of another salt present in the same solution. The object of this line of 



