Dr. Gladstone on Refraction-Equivalents. 



313 



substance has been obtained both in the solid and dissolved con- 

 dition, it is found to be the same. 2nd. Solutions of several organic 

 substances, such as formic and citric acids, give the theoretically 

 correct equivalent for these substances. 3rd. The refraction-equiva- 

 lent of a salt seems to be the same, whether it be dissolved in water 

 or in alcohol. 4th. The refraction-equivalent of a salt in solution is 

 not affected by altering the amount of water in which it is dissolved. 

 5th. The numbers reckoned for these salts in solution bear such a 

 remarkable relation to one another as to force the conviction that 

 they are made up of two components, the one depending on the 

 metal, the other on the substance combined with it. To exhibit the 

 nature and force of this argument, it would be necessary to tabulate 

 a long series of results ; but for the present I shall confine myself 

 to the salts of potassium and sodium, with the corresponding hydro- 

 gen compounds. 



Dissolved compound. 





Refraction-equivalents. 



d o 53 



l °2 











1^1 













Common 









12 ra Ph 



^ a a 



formula. 



.2 o 



CO o, 



1 w 



p 



Fl ° 



n3 B 



fference 

 otassium 

 ium com 



fference 

 otassium 

 rogen co 





£° 



o O 



W° 



S M 



fi^ 



MCI 



18-44 



15-11 



14-44 



3-3 



4-0 



MBr 



25-34 



21-70 



20-63 



3-6 



4-7 



MI 



35-33 



31-59 



31-17 



3-7 



4-2 



MNC 



17-12 











MSNC 



33-40 











MNOg 



21-80 



18-66 



17-24 



3-1 



4-5 



MPOg 





19-48 



18-68 







MHO 



12-82 



9-21 



5-95 



3-6 



6-8 



MC 2 H 5 



27-68 



24-28 



20-89 



3-4 



6-8 



MCH0 2 



19-93 



16-03 



13-40 



3-9 



6-5 



MC 9 H 3 9 



27-65 



24-05 



21-20 



3-6 



6-5 



M 2 C 4 H 4 6 



57-60 



5039 



45-18 



3-6 



6-2 



M.,C0 3 



34-93 



28-55 





3-2 





M.,S0 4 



30-55 



26-20* 



22-45 



2-2 



4-1 



M,Cr 4 7 



79-9 



72-9 





3-5 





M 2 PH 2 2 



26-94 



20-93 





30 







Chloride 



Bromide 



Iodide 



Cyanide 



Sulphocyanide . 



Nitrate 



Metaphosphate . 



Hydrate 



Alcoholate 



Formiate 



Acetate 



Tartrate 



Carbonate 



Sulphate 



Bichromate 

 Hypophosphite. 



From the above numbers several conclusions may be safely drawn. 

 First, it is evident that the refraction-equivalents of the compounds 

 of potassium differ very widely according to the nature of the electro- 

 negative constituents ; again, that the refraction-equivalents of the 

 compounds of sodium differ pari passu with those of the potassium 

 compounds, being always less by a number varying from 3'0 to 3*9. 

 From this it may be fairly concluded that the electro-negative con- 

 stituent has the same effect on light, whichever metal it is united with, 

 and that the refraction-equivalent of potassium exceeds that of sodium 

 by 3'4, or thereabouts. But does the Table afford the data for de- 



* This number seems to be too high, but it is the mean of fairly accordant 

 results. It is rejected in the calculation of average difference between potassium 

 and sodium. 



