28 



THE ABSORPTION SPECTRA OF SOLUTIONS. 



except in length and in the size of the side tube, only the longer cell will be 

 described here. The main part of the cell (T) was made of tool steel and was 

 heavily copper plated and gold plated on all the inner surfaces. 



The side tube was very tightly fitted into the main part of the horizontal 

 tube. The open part of the tube was 1.0 cm. in diameter. The windows 

 of the cell (U, U) were 2.5 cm. in diameter and were either of quartz or glass. 

 One of the troubles with this form of cell is the formation of precipitates on 

 the inside surfaces of the windows. Every time a precipitate is formed, the 

 windows have to be taken out and cleaned. On being put back there is 

 always great danger of the quartz or glass ends being broken. During the 

 work a number of ends were broken in this way. 



Quartz ends are much tougher and less easily broken than glass ends. 

 They are, however, quite expensive and in most of the work the solutions were 

 not transparent in the ultra-violet. For this work glass ends were used. Some 

 of these were cut out of ordinary plate glass and others were made from 



Fig. 3. 



"uviole" glass, which is tougher and much more transparent in the ultra- 

 violet than the ordinary plate glass. For cutting the ends a steel tube was 

 fastened to the axle of an ordinary fan motor. The steel tube was 2.5 cm. in 

 diameter and the motor was placed so that the tube was vertical, the free end 

 of the steel tube being at the bottom. An old glass end was then cemented to 

 a piece of plate glass with hot sealing wax and served as a guide for the steel 

 tube. The plate glass was then held against the end of the steel tube and the 

 motor started. Wet carborundum was fed constantly against the grinding 

 steel tube. Plates nearly 1.0 cm. thick could be cut in this way in 20 or 30 

 minutes. 



The quartz windows rested on gold washers, and these rested directly 

 against the gold-plated shoulders of the tube T. PPP are plungers. Two 

 of these at the ends of the main tube have guide pins that prevent the plungers 

 from turning. Between the plungers and the windows were placed washers. 

 Various kinds of washers of hard leather, lead, zinc, etc., were used. The 



