SYSTEM NAPHTHALENE-CHLOEOBENZENE-PHENOL, ETC. 



15 



ihin rubber cover^^ by closing the stop-cock too early. JV is 

 the layer of paraffine oil floating upon the water to prevent 

 evaporation. 



In order to make observations on the fusion surface of 

 naphthalene, about 10 gramme of it was placed 

 in the inner tube, and phenol or a mixture of JL 



phenol and chlorobenzene was added in succes- 

 sive portions by means of the pipette shown in 

 Fig. 7. After each addition the bath was cooled 

 a few degrees below the supposed fusion point, 

 and forcing in cold air by means of the hand- 

 bellows the fusion point was roughly observed. 

 Then the temperature of the bath was raised to 

 just within ().l°-0.5° of the fusion point. The 



crystal which had separated out was dissolved / I I ^\ 50c.c. 



by passing an electric current through the ring 

 of wire attached to tlie stirrer, and on opening 

 the circuit the rate of cooling was observed for 

 one minute. Then cold air was blown in, the temperature in 

 the inner tube fell 0.1°-0.2° below the fusion point. The stirrer 

 was again set in motion, the minimum temperature was observed, 

 and the time was recorded. In a short time crystals made their 

 appearance in abundance, the maximum temperature and the time 

 were noted. The cooling during the observation of the fusion 

 point was calculated from the rate of cooling already observed, 

 assuming it to be proportional to the temperature difference 

 between the solution and the bath. In this way the quantity 



1) In order to prevent llie nieiciiry from coming into direct contact witli the gas, a 

 thin rubber cover is stretched over the top of the tube containing the mercury and com- 

 municuling below with the reservoir. This device, the invention of an English chemist, 

 proved very advantageous when a very exact regulation of temperature was needed. 



Iff. <- 



