NON-AQUEOUS SOLUTIONS. 

 APPARATUS. 



The spectrograph, spectroscope, photographic materials, etc., used in the 

 study of non-aqueous solutions, were the same as those enr loved in the ear- 

 lier part of this investigation of the absorption spectra of aqueous solutions. 

 Since, however, the various parts of all the cells used for aqueous solutions 

 were fastened together with cement, which was soluble in the alcohol and 

 acetone, it became necessary to design a cell which would not be so acted 

 upon by the solutions to be investigated. Moreover, since no strongly adhe- 

 sive cement could be found, which would satisfy the requirements of being 

 insoluble in water, alcohol, acetone, etc., it was decided to construct a cell of 

 entirely new design which would be absolutely free from cement of any kind. 



A vertical section of the cell is shown by plate 22, and the details of the 

 several parts may be explained as follows: In its fundamental principles 

 the cell consisted of three distinct parts: (a) An outer glass tube with a 

 quartz bottom to hold the liquid; (b) an inner glass tube with a quartz plate 

 at the lower end to regulate the depth of the liquid and to cause the upper 

 surface of the absorbing layer of solution to be both plane and parallel to the 

 quartz bottom of the larger glass tube; and (c) a mechanism which would act 

 as a stopper to the system of glass and quartz just mentioned, and which 

 would also enable the experimenter to adjust the cell for any desired depth 

 of absorbing layer from zero to the full capacity of the cell, i. c., about 3.5 cm. 



The separate parts of this piece of apparatus will be described in the order 

 in which they would be assembled for actual use. M denotes a plane parallel 

 plate of quartz, ground carefully in the form of a frustum of a cone, so as to 

 fit very accurately into the conical hole at the lower end of the glass tube D. 

 The thickness of this quartz plate was 4.6 mm. and its least diameter was 12.6 

 mm. The glass tube was blown with a thick shoulder at its upper end. 

 The plate M was first slipped into place in the tube D, and then the rubber 

 washer G w-is pushed down against the quartz by introducing the brass tube 

 C into the glass tube. In order to prevent dust from entering the inner 

 tubes, the plane parallel quartz plate A was permanently set into a cylin- 

 drical depression in the upper end of the brass tube C. This plate was 

 2 mm. thick and 20 mm. in diameter. 



The brass tube widened out into a sort of plate at its upper end, and this 

 projection was pierced by three holes at the vertices of an equilateral triangle. 

 Through these holes suitable screws passed, and one of these is shown at B 



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