CONSTITUTION OF 
Royal College of Science, Dublin. 
[ oe J 
WADUL, 
THE ACTION OF HEAT ON THE ABSORPTION SPECTRA AND CHEMICAL 
SALINE SOLUTIONS. 
(Plates XVII. to XXII.) 
[Read Frsrvary 21, 1900. | 
By W. N. HARTLEY, F.RB.S., 
CONTENTS. 
PAGE PAGE 
Introduction, . . 258 Photographed Spectra of Didymium Sulphate, 
Early experiments of Schonbein, yon Babo, ‘and Schiff, Praseodym Ammonium Nitrate, and Nest 
on the constitution of Saline Solutions, . 254 ammonium Nitrate, . 290 
Researches of Gladstone, Bunsen, Melde, Burger, H.W. Recent experiments of Muthmann and Stiitzel on 
Vogel, Landauer, Morton and Bolton, and Russell, Neodym and Praseodym Salts, and of Ostwald 
on the Absorption Spectra of Solutions, . 284 on Permanganates discussed, . 292 
Method of Experimenting, 256 Deductions and Conclusions, 293 
Pawn Ti The Spectrum of Potassium Permanganate de- 
; scribed and measured, 294 
The Absorption Spectra of Nickel and Copper Salts 
described and measured, 258 | Parr Y. 
Spectra of Anhydrous Substances and Salts not 2 The Molecular Constitution and Dissociation Pheno- 
dehydrated! at 100° C:, coe mena of Saline Solution 
The molecular weight of Anhydrous Haloid Salts oe ee 
determined by hegdanann s method, 961 The action of different Solvents, 296 
The Composition of the Hydrates of Nickel Bro- The effect of heat on the Absorption Spectra. 
mide and Iodide determined, : . 262 Conclusion I., 297 
Reactions of Salts in solution at different tempera- 
Part II. tures, 298 
Spectra of Cobalt Salts described, 267 Conclusion II., . 298 
Method of photographing the Absorption Spectra i in Crystallized Hydrates generally dissolve in cold 
the region of Coloured Rays, . 268 water without dissociation of the Molecule. 
Varying ‘limits of accuracy in the measur ements of Conclusion III., 298 
Absorption Spectra, . 269 Dehydration of a Gr ystalline Hy drate in an Aqueous 
Cobalt Salts form Oxychlorides, Oxybromies, and Solution by Alcohol and the recrystallization of 
Oxyiodides, 278 the original Salt on Evaporation, 5 . 3800 
eee that the Haloid Salts are inot Hy drolysed, 278 No evidence of Alcoholates being formed. Experi- 
ments of Potilitzin on Cobalt Chloride, 3801 
Parr ITT. Tabulated statements of the changes in colour of 
The action of heat on the Absorption Spectra of Aqueous Solutions of Salts, &., : 302 
Chromium Salts. Measurements of Spectra, 279 Evidence of several Hydrates of the one Salt 
Change in the Chemical Constitution of Chromium being simultaneously present in the same Solu- 
Salts when their solutions are heated, 281 tion, 803 
The experiments of Schrotter, Kruger, and Lew el Remarkable behayiour of Cuprie Bromide, 303 
discussed, : 283 Conclusions IY. and V., 304 
Thermo-chemical researches of Recoura on the The colour relations of Solid Salts to those of the 
Constitution of Chromium Salts, F 286 same substances in Solution, 3804 
Chromoxalates and Chromo-sulphates, their con- The most stable Hydrates in concentrated Solutions 
stitution, . 287 of Cupric Chloride and Bromide, and Nickel 
Lapraik’s investigation of the Spectra of Chromium Bromide and Iodide, 806 
Salts, and evidence of the existence of two Evidence of the Compounds formed in some 
Chromoxalic Acids, 287 Aqueous Solutions, 806 
IV. Reference to Riidorff’s, De Coppet’s, and Thomsen’s 
Part experiments on the formation of Taguig Boy 
Spectra of Salts of Uranium, pidymia, and Per- drated Salts, 307 
manganates described, 287 Conclusion VI., 307 
Measurements of Spectra of various “Didymium Conclusion VII. ., and references to Ostwald’s and 
Salts, . 288 Ewan’s Observations on the eee Rpectra 
Reference to the Investigation of Bunsen and of of very Dilute Solutions, . 307 
H. Becquerel, : 289 Summary and General Conclusions, - 808 to 312 
Introduction. 
In the years 1874-75 the Secretary of the Royal Society (now Sir George Gabriel 
Stokes) did me the honour of presenting for publication two papers with the 
TRANS. ROY. DUB. SOC., N.S. VOL. VII., PART 
VIII. 
2N 
