RESULTS. 



105 



SUMMARY. 



The transmission and reflection spectra of at least 125 elements and 

 compounds have been examined, many of them to 15 p, by means of a 

 mirror spectrometer, a rock-salt prism, and a Nichols radiometer. The 

 aim of the investigation was the study of a series of minerals containing 

 oxygen and hydrogen in the form of what is known as water of consti- 

 tution and water of crystallization. The interpretation of the results 

 are based upon the assumption that if the union of the oxygen and the 

 hydrogen in the molecules is similar to that of water, then the absorp- 

 tion spectra of minerals, containing these two elements thus united, 

 should show the absorption bands of water superposed upon the absorp- 

 tion spectrum of the other constituents. 



On the other hand, minerals containing oxygen and hydrogen as 

 water of constitution should not show the water bands, except hydrox- 

 yls, which should show a band at 3 p. 



The results show that of some 30 minerals containing "water of 

 crystallization" there are no important exceptions to the rule that they 

 should show the bands of water. On the other hand, the one important 

 exception to the rule that minerals containing ''water of constitution" 

 should not show water bands is cane sugar. Minerals containing 

 hydroxyl groups generally have a marked band at 3 /*. Sulphates have 

 a strong band at 4.55^, and a less constantly recurring band at 9.1 /JL, 

 due to the SO 4 ion. On the other hand, the silicates do not have such 

 definite bands, which would seem to indicate that the union of the 

 silicate radical is different in each mineral containing that element. In 

 Table III are given a list of groups of atoms which have characteristic 

 absorption bands. 



TABLE III. 



The examination includes minerals of which the chemical constitu- 

 tion is in doubt; for example, talc and serpentine. The former is not 

 supposed to contain hydroxyl groups, while in the latter such groups 

 are inferred. The present research supports these views in that the. 

 transmission curve of talc does not contain an absorption band at 3 M, 



