//. K Merwin — Density of Minerals. 



427 



empirical formula which gives the density, 4 d, between 2-25 

 and 3-40 at 20° with a maximum probable error of ±*002. 



d = 5-39(w— 1-5467) + 2-25 



which in a simpler form is d = 5 - 39w.— 6-0865. For accurate 

 work, if the temperature is more than 3° from 20° a correction 

 for d of --001 for each 2° below 20° and of +-001 for each 

 2° above 20° should be made. 



Density at 20° C. 

 3-449 



Table I. 



Refractive index 

 1-7686 



3-396 . 





1-7590 



3246 





1-7312 



3-180 





1-7195 



3-046 





1-6944 



2-980 





1-6823 



2-748 





1-6391 



2-649 





1-6207 



2-648 





1-6205 



2-367 





1-5685 



2-163 





1-5320 



2-067 





1-5148 



V. Goldschmidt 6 constructed a similar table for a solution of 

 potassium-mercuric iodide. The standard solution is difficult 

 to prepare and maintain. 



At given densities the observed refractive index varied with 

 the temperature as follows: 



Density. 

 2-067 



2-367 



2-748 



C3-449 



Refractive index. 



Temperature 



j 1-5147 

 I 1-5150 



23 

 20 



j 1-5695 

 ( 1-5685 



14 



20 



j 1-6398 

 ( 1-6391 



13 



20 



j 1-7690 

 ( 1-7686 



16 

 20 



In using the cell with the refractometer it is more conven- 

 ient to use only one part of the vertical circle scale. If 

 accuracy within ±'002 is desired, it is then necessary that the 



4 The formula between 2 - and 2-25 is d=5 - 7n— 6'567, and between 3-4 

 and 35 is c7=552n-6-313. 



5 N. Jahrb. f. Min., Beil.-Bd., i, 234, 1881. 



