4 MI: n.m: rrniMi-.KTsoN \M> \i.\n.i: ITTIIKKKTSON ON Tin- 



be ih- t.. tin- introduction of a new free period, or the elimination of an old our, 



previously wrap|-l up i" "A '"'' "..V 



^ nnvtry qf HemJtf. Before proceeding to give the experimental work it will }>e 

 eonvi-nii'nt t<> Niimmaris.- tlie results obtained : 



(1) In hydrochloric, hydrobromic, hydriodic acids, sulphur dioxide* and sulplm- 

 n-tt.-d hydrogen* tin- refractivity of the compound is less than thr sum of 

 tin- ivtra<-tivitit-.s of tin- tlt-im-nts, and the dispersive power of the compound 

 lie* Ix-twccii those of its constituents ; 



rJi In nitrous oxide, nitric oxide, ammonia, and ozone the refractivity of the 

 compound is greater than the sum of those of its constituents, and the 

 dispersive power is greater than that of either constituent ; 



(3) In steam the refractivity of the compound is less, and the dispersive power 



greater, than those of its constituents ; 



(4) In all cases the change in dispersive power is great relatively to the change in 



refractive power. 



We hav- framed a hypothesis which, in our opinion, would account for these 

 changes in a qualitative manner, and we hope to puhlish it elsewhere. 



CHLORINE. 



-Tlie refractive index of gaseous chlorine has only been measured 

 IH-|...Mst found M -l== "000772 for white light with gas, prepared from 

 MnO,, whose density was 2' 47 (air l). 



MASCART} found -! == "000768 for white light. He worked at low pressures at 

 tin- temperature 12 C. and compared the refractivity with that of air under the 

 vuiie condition.-,. 



ITie dispersion of the gas has not previously been measured. 



-The gas we used was prepared by dropping strong hydrochloric 



potassmm jK-rmanganate. After washing in water and drying by sulphuric 



feed in a hath of acetone cooled with solid C0 2 and then allowed to 



the air , tl,, oonn.cting tubes had been displaced. The refractometer 



My ,-va,uated, was then placed in connection with the chlorine by a 



tube so fi, lt - that the gas entered the tube sufficiently slowly for the 



Wndn to be ,ount,l. When the pressure of gas in the refLtometer 



-* 



;: 



