CHEJMISTRY — BAXTER, JONES. 149 



of iodine peutoxide. Pure iodic acid was made by the action of fuming 

 nitric acid upon iodine in quartz vessels. The iodic acid, after crystalliza- 

 tion in quartz vessels, was dehydrated in a current of dry air and the result- 

 ing pentoxide was weighed. Then it was dissolved in water, reduced with 

 sutphurous acid, and titrated against the purest silver. This investigation 

 is still in progress, 



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

 No. 267. Investigations on hydrates in concentrated aqueous solutions. 

 (For previous reports see Year Book No. 2, p. xxx ; Year Book No. 3, 

 p. 106, and Year Book No. 4, pp. 151-152.) $1,000. 



During the past year a study has been made of the absorption spectra of 

 such salts as cobalt chloride, copper chloride, and copper bromide, as affected 

 by the presence of certain colorless salts with large dehydrating power, such 

 as calcium chloride, calcium bromide, and aluminium bromide. The object 

 of this part of the investigation, which has now been in progress several years, 

 was to see what evidence could be obtained for or against the present hydrate 

 theory proposed about six years ago, from a study of the absorption spectra 

 of certain colored substances as affected by the presence of other substances 

 which have even greater power to combine with water than the colored sub- 

 stance in question. By adding the colorless substance in different quanti- 

 ties we hoped to throw light on the relation between hydration and mass 

 action. 



A Hilger prism spectroscope was used for observational work, and a 

 grating spectrograph for the photographic records. The solutions were 

 placed in cells provided with quartz ends, so as to be able to obtain results 

 also in the ultra-violet region. 



The freezing-points and conductivities of many of the solutions were also 

 measured. 



Very satisfactory spectrograms were obtained, showing the change in the 

 absorption spectra of cobalt chloride, cobalt bromide, and aluminium chloride; 

 by the addition to solutions of each of varying amounts of calcium chloride, 

 calcium bromide, and aluminium chloride. 



The wave-lengths of the absorption bands in all of the 34 spectrograms 

 were carefully measured. The results from aqueous solutions are entirely 

 unambiguous as bearing upon the hydrate problem. The color changes in 

 the solutions are not due to the presence of double salts, as Engle supposed. 

 They are not to be accounted for on the basis of ionization, as Ostwald had 

 thought. They are not due to the presence of complex ions, as Donnan 

 supposed, but to a change in the hydration of the colored salt or the ions 

 resulting from it. 



The evidence furnished by the spectroscopic work for the general correct- 

 ness of the present hydrate theory seems to be conclusive. Indeed, the 

 interpretation of the spectrograms in terms of this theory is perfectly simple, 



