5O INFRA-RED TRANSMISSION SPECTRA. 



assumption of a larger dispersion, and a longer column of air traversed 

 by the rays, which would intensify the CO 2 band at 2.75 //,. 



From the muscovite curve, however, it will be noticed that the air 

 (CO 2 ) band would be intensified by that of mica at 2.85 /*. 



SERPENTINE (H 4 (Mg,Fe) 3 SiO,). 



(Massive; subtranslucent ; curve a, t = 0.225 mm; curve b, f = o.o8 mm. Fig. 36. 



From Montville, New Jersey.) 



In serpentine the water is chiefly expelled at red heat. According to 

 Miers, 1 talc and serpentine are to be regarded as basic and not hydrated 



10 



I 23456789 



f 



FIG. 36. Talc (c) ; Serpentine. 



silicates, since they part with their water only at a high temperature. 

 From the curve of serpentine, which shows a large absorption band at 

 3 /t, if the results from the present method of examination are to be 

 trusted, it would appear that there are hydroxyl groups present. 



From the results obtained by Clarke and Schneider 2 it was inferred 

 that the Mg is present as MgOH, and hence the formula is written 

 H 3 (MgOH), Mg 2 (SiO) 2 . It has also been written with two mag- 



1 Miers : Mineralogy, p. 439. 



2 Clarke and Schneider : Amer. Jour. Sci., 40, p. 308. 1890. 



