186 Prof. Mitscherlich on the Spectra of Compounds 



If, as in the case of the calcium compounds, the distance of 

 the lines in the spectrum of fluoride of strontium is calculated 

 from that of bromide of strontium, we obtain the equation 



x 123-8 

 fr5 = 6*8 "i from which *=12-8. 



From observation #=18. Hence, as in the case of fluoride of 

 calcium and fluoride of barium, this does not agree with calcu- 

 lation. 



The iodide-of- strontium, like the iodide-of-barium spectrum, 

 I could not observe. According to the following equations, 

 which are formed as in the case of barium, it has been calcu- 

 lated : — 



x 123-8 , 



?r-p = iwrv , irom which a?=4*7* 

 b'o l/U'o 



From the distances and from the position of the starting-point, 

 we obtain the following equation for the position of the lines for 

 iodide of strontium : — 



Distance of the first bromide- of- strontium line 



from the starting-point 1 



Distance of the first iodide-of-strontium line y 

 from the starting-point 



Distance of the second bromide-of-strontium line 



from the starting-point 7 



~~ Distanceofthesecondiodide-of-strontiumlinefrom z/ + 4'7 

 the starting-point 



from which y = 0'67. 



Hence the first line of iodide of strontium is at the division 

 137-3, and the other at 132'6. The position of the other bright 

 lines of the iodide of strontium which lie between the two has 

 been calculated in the same way. 



Hence for the haloid compounds of barium, excepting fluoride 

 of barium, it follows that the distances of corresponding lines in 

 their spectra are directly proportional to the atomic weight, and 

 that for the haloid compounds of calcium and strontium, except- 

 ing the fluorides, these are inversely proportional to the atomic 

 weights. Further, that the relation of the line nearest the 

 starting-point to the same, to the distance of the furthest line, 

 is the same for the same metal in the case of the haloid com- 

 pounds of barium, strontium, and calcium. Here also the fluo- 

 rides are to be excepted. 



I hope I shall hereafter succeed in finding the reason for this 

 abnormal relation of the fluorides. 



The fact appears important to the significance of the starting 



