IO4 INFRA-RKD REFLECTION SPECTRA. 



POTASSIUM SULPHATE (K a SO 4 ). 



Curve b, fig. 88, is for a saturated solution of this compound. There 

 appear to be two maxima a small one at 9.1 p, and a much larger one 

 at 9.4 fji which disagrees with Pfund, who found a maximum at 8.85 

 for the reflection from the plane surface of a mass of these crystals. 



The results, as a whole, show that the single narrow reflection bands 

 of several of the sulphates at 9 ^ is complex, and is shifted toward the 

 long wave-lengths when dissolved in water, while in others this band 

 remains single, and is not shifted in solution. The reflection of most of 

 the solids was found by Pfund (loc. cit.). In some cases we agree in 

 the location of the maxima, while in other cases (solids vs. solutions) 

 we do not agree. This is not, in any inherent errors, in adjustment of 

 the present instrument, for at the conclusion of the work the quartz 

 band at 9.05 /j. was found at its proper place, as shown in fig. 86. 

 Neither is it due to errors in Pfund's apparatus (although his dispersion 

 was not so great), for we agree in the position of the maxima of quartz, 

 glass, Iceland spar, potassium nitrate, copper sulphate, and sulphuric 

 acid. The solutions were examined on the same day and in the follow- 

 ing order: H,SO 4 and the sulphates of Cd, Ni, Cu, Zn, K, Na. The 

 disagreement is in Ni, Zn, K, Na, which means that the instrument 

 could not have gotten out of adjustment during the examination. 



The conclusion to be drawn is that several of these sulphates, viz, 

 Ni, K, Na, and possibly Cd, are dissociated, or that the intra-molecular 

 condition of the molecule (the "bonding") has become similar to that 

 of H 2 SO 4 . Possibly hydrates have been formed. But what may we say 

 of the sulphates of Ba, Sr, and Mg, which in their solid (anhydrous) 

 condition have several bands, some of which lie close to those of H 2 SO 4 ? 



The more logical w r ay of attacking this problem would have been to 

 examine 1 the solid crystals at the same time as the solutions ; but life 

 is too short for one man to do all this, and the aforesaid line of reason- 

 ing excludes the possibility of the disagreement being due to instru- 

 mental errors, which would have to amount to from 4 to 6 min. of arc 

 to account for the shifting of some of the maxima. In Cu and Cd the 

 shift, if any, is very slight, although the Cd band is evidently complex. 



In the sulphates of Ni, K, and Na a definite shift has been noted, and 

 is similar to the effect observed in solutions of iodine in CS 2 , and in 

 C,H 5 OH in the visible spectrum. No doubt a solvent may exist, in 

 which the 9.1 \i band of CuSO 4 is also complex. 



1 Since writing this the author has examined the sulphates of Ni and Cu in the 

 solid state and in solution. The maximum of solid CuSO* and of the solution in 

 water occurs at 9.12^, while in NiSO 4 the complex band of the solid at 8.9 to 

 9.15 ji is shifted to 9.2 to 9.5 ^ in solution. 



