Displacement in their own Mother-liquor 205 



was during the period over which the experiments were spread. 

 All the experiments were made between the I2th and 22nd of 

 July, 1904, with the exception of those on caesium bromide, 

 which were made on August loth. By that time the anti- 

 cyclone had begun to break and the value of T for this salt is 

 21-4 C. For all the other salts, T lies between 22-8 and 24-3 C. 



During the whole of the period the barometer was very 

 steady, varying between 758 and 761 millimetres, and the 

 relative humidity of the air varied between 40 and 50 per cent. 



Of the three values D lt D 2> D 3 for the specific gravity of 

 the salt, Dj is obtained directly from the first portion of the 

 salt, D 2 from the sum of the two portions, and D 3 is derived 

 from Dj and D 2 by subtraction. 



D 2 represents very nearly the mean of D l and D 3 and is the 

 accepted value for the majority of the salts. It is expressed 

 to three places of decimals, of which units in the second place 

 are exact. 



It will be noticed that in the case of rubidium chloride the 

 value of Z>! is accepted. The second determination depends 

 on the approximate weight of the second portion of salt when 

 the tube was being filled, the exact weighing on the balance of 

 precision having been accidentally omitted. The operation 

 was however completed, and the calculation made with the 

 approximate weight was used as a control. The result shows 

 that the value of D^ may be safely accepted. In case of 

 potassium chloride the value of D 3 (1-951) is accepted, and the 

 reason for this is as follows: The first portion of salt was in 

 very coarse powder, and in mixing it with the mother-liquor 

 numerous crystalline particles were observed which contained 

 gaseous enclosures, easily perceptible by the naked eye. As 

 was expected, the observed specific gravity proved to be low. 

 second portion was much more finely powdered and tin- 

 specific gravity resulting from the two was higher (1-8872). 

 But this result is affected to the full extent by the gaseous 

 enclosures in the first portion. We therefore calculate the 

 specific gravity from the second portion alone, which gives 



,10 for the specific gravity. 



Discussion. It is an advantage of the method just described 



