Displacement in their own Mother-liquor 201 



salt. It is at this temperature also that the specific gravity 

 bottle is weighed when filled with distilled water and with 

 mother-liquor respectively. In fact the temperature of equi- 

 librium and of separation is the only temperature used. 



In Table I (p. 202) the experimental details are given in full 

 in the case of one salt, namely, caesium chloride. For the other 

 salts the results only are given, and they are collected in 

 Table II (p. 206). 



All the weights given in this paper represent the weight 

 in vac no. 



The specific gravity bottle which was used was one of the 

 common and convenient form which has a thermometer for a 

 stopper and a lateral capillary tube for the adjustment of level. 

 Its nominal capacity was fifty cubic centimetres. On three 

 occasions one of 25 c.c. capacity was used for determining the 

 displacement of the mother-liquor. 



The concentration (m) of the mother-liquor is determined 

 by titration with tenth-normal silver nitrate solution. This 

 solution was made with the greatest care and contained exactly 

 17 grammes of silver nitrate in one litre, at the ordinary tem- 

 perature of the laboratory at the time. The burette used was 

 divided into tenths of a cubic centimetre and had a capacity 

 of 50 c.c. The determination of the halogen was not made 

 until the specific gravity had been determined, and, if the 

 concentration was not already known within narrow limits, a 

 preliminary titration was made, after which the volume of 

 mother-liquor was weighed, which would certainly require 

 40 + i c.c. for titration. The capacity of the burette from 

 o to 40 c.c. was determined by weight with great care. The 

 concentration is stated in gram-molecules salt per 1000 granim - 

 of water. 



For weighing out the salt and passing it directly into the 

 specific gravity bottle a special and convenient form of weighing 

 tube was used. It was made out of a stoppered specimen tube 

 with an internal diameter of two centimetres and a length of 

 seven or eight centimetres. The lower end of this tube was 

 opened and a piece of thin glass tube joined to it before t h 

 blowpipe. This tube, which had a length of about three 



