212 REPORTS OF INVESTIGATIONS AND PROJECTS. 



dichromate the solution was titrated against a weighed equivalent amount 

 of silver and then the silver bromide was collected and weighed. 



Preliminary experiments indicate the value 55.85 for the atomic weight of 

 iron, if silver is assumed to have the value 107.88. The result is essentially 

 identical with that previously obtained by Baxter with ferrous bromide which 

 had been sublimed in porcelain tubes, and which contained a small quantity 

 of alkali extracted from the tubes. This investigation will be continued with 

 several samples of iron, including meteoric iron. 



Mr. W. A. Worsham continued the investigation upon the atomic weight 

 of lead (see Year Book No. 6, p. 185). At first the attempt was made to 

 synthesize lead sulphate quantitatively. This salt, when precipitated from 

 even very dilute solutions, occludes soluble lead salts to a very marked de- 

 gree. Attempts to eliminate the occluded salts by fusion of the lead sulphate 

 in a current of sulphur trioxide failed because of the dissociation of the tri- 

 oxide at temperatures above the fusing point of the salt. Hence lead sul- 

 phate was finally rejected as entirely unsuited for exact analysis. Lead 

 bromide was next selected for investigation. Some difficulty was experienced 

 in obtaining salt free from insoluble basic impurities. This was finally ac- 

 complished by fusing, in a current of nitrogen and hydrobromic-acid gases, 

 salt which had been recrystallized from hydrobromic-acid solution. No ana- 

 lytical results have yet been obtained. 



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

 No. 557. Investigations of the absorption spectra of solutions. (For 

 previous reports see Year Books Nos. 2, 3, 4, 5, 6, and 7.) $1,200. 



The work during the present year has had to do with three problems : ( i ) 

 The study of the absorption spectra of certain potassium salts containing 

 colored anions; (2) the absorption spectra of uranyl salts; (3) the effect of 

 temperature on the absorption spectra of salts of a number of metals. 



The work with potassium salts included potassium ferrocyanide, potassium 

 ferricyanide, potassium chromate, and potassium dichromate. The appara- 

 tus used in this part of the work is essentially the same as that employed by 

 Jones and Anderson.* Light from the arc or Nernst filament was passed 

 through the solution in a glass vessel closed at both ends by plates of quartz. 

 The vessel is made by inserting one glass tube into another through a cork, 

 and thus the depth of the solution through which the light is allowed to pass 

 could easily be regulated. The work with the potassium salts has had to do 

 especially with testing Beer's law for these solutions. If Beer's law holds for 

 the absorption spectra of a given substance, then if we increase the dilution 

 of the solution and at the same time keep the amount of colored matter in 

 the path of the beam of light constant, the absorption bands should not 



♦Publication No. no, Carnegie Institution of Washington. 



