Chemistry and Physics. 295 



under the name anthochroite is not confirmed by this analysis 

 inasmuch as there is a marked difference in the ratio of the 

 alkalies to the sesquioxides. As may be seen from the ratio in 

 the author's analysis the alkalies and sesquioxides are present 

 in the proportion 1 : 1, suggesting a molecule of the jadeite 

 type, while MgO and CaO are also present as 1:1 as in 

 normal diopside. Taking from the total ratio Na 2 : R 2 3 : 

 SiO„ = -021 : -021 : '084 = 1:1:4, there remains MnO + MgO 

 +CaO : Si0 2 = -846 : 815 = 1'04 : 1 or nearly 1 : 1 as required 

 by diopside. The composition of violan may therefore be 

 expressed as a mixture of the following metasilicates. 



Diopside MgCa(Si0 3 ) 2 90-8 per cent. 



•Jadeite NaAl(Si0 3 ) 2 4-1 



Acmite NaFe(Si0 3 ) 2 2-4 " 



? NaMn(Si0 3 ) 2 2-7 " 



The mineral is therefore essentially a blue variety of diop- 

 side, containing small quantities of various well recognized 

 pyroxene molecules. 



An azure blue pyroxene has recently been described by 

 Merrill and Packard* from the Middle Gila, New Mexico. 

 Their analysis corresponds essentially tc a normal diopside, 

 with only I'll per cent of FeO and the blue color is regarded 

 by them as due to the ferrous iron. 



Laboratory of Mineralogy and Petrography, 

 Sheffield Scientific School, June, 1893. 



SCIENTIFIC INTELLIGENCE. 

 I. Chemistry and Physics. 



1. On the Absorption-spectra of Copper salts. — The absorp- 

 tion-spectra of aqueous solutions of copper chloride, sulphate 

 and nitrate have been examined by Ewan, using Kruss's uni- 

 versal spectrometer for the purpose and employing Vierordt's 

 method. The conclusions reached in the investigation may be 

 summed up as follows : (1) On diluting their solutions the ab- 

 sorption-spectra of all the three salts examined are observed to 

 change ; (2) the character of these changes is such as to show 

 that the spectra, in dilute solutions tend to become identical ; 

 (3) the behavior of the salts examined leads to the conclusion 

 that in strong solutions, the acid and basic parts of the salts are 

 associated in producing absorption of light whilst in dilute solu- 

 tions they act independently in doing so ; (4) these results are 

 substantially in agreement with the hypothesis of electrolytic 

 dissociation ; (5) and finally the results obtained do not seem to 



* This Journal, III, xliii, 1892, p. 279. 



