Section ]^. 



CHEMISTRY AND MINERALOGY. 



President of the Section : 



W. M. HAMLET, F.I.C., F.C.S., Government Annlyst of New 



South Wales. 



1.— THE OLEO-REFRACTOMETER IN ORGANIC 

 ANALYSIS. 



By W. M. HAMLET, F.I.C., F.C.S. 



An optical method of chemical analysis, founded on the well- 

 known fact of the refraction of light on entering transparent 

 bodies at an oblique angle, has lately been devised by M. 

 Ferdinand Jean, Director of the Municipal Laboratory in 

 Paris, and improvements added by M. Amagat. 



The law that the sine of the angle of incidence is in con- 

 stant ratio with the sine of the angle of refraction gives the 

 index of refraction, and as this differs in different media, it 

 would appear that the specific refractive power of a substance 

 is dependent on the chemical nature of the body examined. 



The index of refraction is, as Ostwald has pointed out, the 

 numerical value of the time required by light to pass through 

 a given distance in the liquid under examination. Knowing, 

 then, the time value for a standard of known composition, it 

 follows that deviations from the normal refractive indices of 

 compounds must indicate variation in their composition. 



The oleo-refractometer has been found useful in the ex- 

 amination of butters, fats, oleomargarine, oils, naphthas, 

 methylated spirits, and various other articles of commerce. 



Dr. Muter first described this instrument in the Analyst,* 

 and, being favourably impressed with the use of the instru- 

 ment which I exhibit here before you, it may prove of interest 

 to the members of this section of the Association. 



The use of the refractometer being first applied to the 

 examination of oils, it was called the oleo-refractometer by 

 its original inventors, MM. Amagat and Jean. 



Ellinger, Jour. Chem. Soc, LX., p. 1305, prefers to call 



Analyst, Vol. XV,, p. 87. 



