1887.] 



Dispersion Equivalents. 



401 



Paramyosinogen, myosinogen, and myoglobulin are proteids of the 

 globulin class. They are all completely precipitated by saturation 

 -with magnesium sulphate, or sodium chloride, or by dialysing out the 

 salts from their solutions. They can be separated by fractional heat 

 coagulation, or by fractional saturation with neutral salts. 



When muscle turns acid, as it does during rigor mortis, the pepsin 

 which it contains is enabled to act, and at a suitable temperature 

 (35 — 40° C.) albumoses and peptones are formed by a process of self- 

 digestion. It is possible that the passing off of rigor mortis, which is 

 apparently due to the reconversion of myosin into myosinogen, may 

 be the first stage in the self-digestion of muscle. 



XX. " Dispersion Equivalents. Part I." By J. H. GLADSTONE, 

 Ph.D., F.R.S. Received May 24, 1887. 



The idea of refraction equivalents has become familiar to those who 

 work on the borderland of optics and chemistry, and the value of that 

 property as a means of investigating the chemical structure of com- 

 pounds is becoming more and more recognised. There is a similar 

 property, perhaps equally valuable for the same object, which has 

 attracted little attention hitherto ; I allude to the equivalent of 

 dispersion. During the last twelve months, however, I have collated 

 old measurements of the length of the spectrum, whether made by 

 myself or by others, and have added many new determinations, and I 

 am now in a position to submit some of the results to the Society. 



The history of the subject goes back to the first paper of Mr. Dale 

 and myself upon the refraction of light,* in which we gave as one of 

 the conclusions " the length of the spectrum varies as the temperature 

 increases." In our second paperf we came to the conclusion that 

 "there is no simple relation holding good for different liquids between 

 the increase of volume and the decrease of dispersion by heat," con- 

 trary to what we found to be the case with refraction. We adopted 

 ^"/"a* i- e -i the difference between the refractive indices for the 

 solar lines A and H as the measure of dispersion. This divided by 

 the density gave the specific dispersion. When, however, Landolt 

 adopted the plan of calculating the " refraction equivalent," we 

 applied the same method to what we termed the dispersion equivalent, 



that is, " the difference between P ^ A , ^ and ~P ^ H , \ or more simply 



* " On the Influence of Temperature on the Eefraction of Light." ' Phil. 

 Trans.,' 1858, p. 8. 



f " On the Refraction, Dispersion, and Sensitiveness of Liquids." ' Phil. Trans.,' 

 1863, p. 323. 



2 G 2 



