INDUSTRIAL PROGRESS DURING THE YEAR 187G. Ixi 



H. Vogel has published additional facts concerning the effect of 

 certain coloring matters upon the sensitiveness of silver bromide to 

 different portions of the spectrum. He finds, for example, that a di- 

 lute solution of methylrosaniline picrate increases powerfully this 

 sensitiveness for the red rays between B and C. He says (1) that 

 pure silver bromide is sensitive even to the ultra-red rays ; (2) that 

 to the substances already enumerated as increasing the sensitiveness 

 of the bromide for special parts of the spectrum must be added 

 methyl violet and cyanin, the latter increasing it for the orange rays ; 

 (3) that it is better to flow the alcoholic solution of the coloring 

 matter ou the collodion ; and (4) that too strong a solution is to be 

 avoided. 



Vogel has also made an examination of the absorption spectra of 

 several salts of the iron group of metals, and has drawn the charac- 

 teristic absorption curves which belong to them, with a view to util- 

 ize the sj)ectro- analytic method in qualitative analysis. By this 

 means he has detected permanganate in a layer one and a half cen- 

 timeters thick of a solution which contained only -^soVo o P^rt. 



The same author has given the results of his examination of the 

 spectra of various coloring matters, with especial reference to their 

 use for detecting these substances when used for adulterations, es- 

 jDccially in wines. These substances are very numerous, not less 

 than 482 having been mentioned for this purpose at the recent 

 Wine Congress in Colmar. Vogel uses a common pocket spectro- 

 scope, a few test tubes, and some simple reagents. Upon a horizon- 

 tal line as the axis of abscissas he erects jDerjoendiculars at the posi- 

 tions of the Fraunhofer lines, and then, by means of ordinates pro- 

 portional to the intensity of color at different points, he obtains a 

 simple intensity curve by which the results may be very readily 

 compared. Figures of many of these curves are given in the paper, 



Sauer has experimented upon the visibility of the ultra-violet rays 

 of the spectrum. He used for this purpose light emitted by zinc in 

 the electric arc, which he observed was particularly rich in these 

 rays. He thinks there would be no great difficulty in using this 

 method for obtaining a photograi^h of this portion of the spec- 

 trum. 



Lockyer has made some remarkable observations on the spectrum 

 of calcium at different temperatures and under different conditions. 

 The blue line ordinarily observed in the calcium spectrum given 

 with a Bunsen burner he considers a line of calcium itself, the other 

 lines being those of its chloride, not dissociated. As the dissocia- 

 tion advances by rise of temperature, the blue line becomes more 

 brilliant and the chloride spectrum fades. If now the electric arc 

 be employed, the blue line is intense, and two new lines appear in 

 the violet which occupy the position of the two H lines in the sun 

 spectrum. But while in this spectrum tlie blue line is the most in- 



