On the Waters of the Salt Lake of JJrmi. 



315 



loss of water vapour and consequent concentration. The temperature 

 was measured by a form of platinum resistance thermometer, which 

 reads to 0*01° C. Three readings were always taken. Firstly, the 

 temperature of the steam from ordinary boiling water in a steam jacket 

 and under atmospheric pressure; secondly, the temperature of the 

 boiling salt water ; and finally, the temperature of steam once more. 

 If the first and last readings were identical, it was considered that the 

 conditions of the experiment had remained constant. As a matter of 

 practice it was found that when once the boiling point of the salt 

 water had been reached, the water continued to boil at that tempera- 

 ture for any length of time, so long as the pressure remained constant. 



A. B. 



Boiling point under normal pressure 103-84° C. 103*88° C. 



! It will thus be seen that the three results of the physical examina- 

 tion of the two samples A and B are all mutually confirmatory, in so 

 far that they indicate that sample B had become a little more concen- 

 trated than A during its journey from Persia to Oxford. 



Chemical Examination. 



The method adopted was that of Dittmar, as described in the 

 Beport on the Composition of Ocean Water.* 



For the estimation of the lime and magnesia, 20 c.c. of the water, 

 weighing approximately 22*2 grams, were measured off, and the quan- 

 tities used in the determination of the potash and total salts were half 

 that amount. 



Examination of the Correctness of Dittmar 's Factor 0*91 for " Crude " 



Lime. 



Forty c.c. of the water were measured off and weighed. In accord- 

 ance with Dittmar's recommendation, the calcium was precipitated as 

 oxalate, filtered, washed, and finally weighed as oxide. The " crude " 

 oxide obtained amounted to 0*0319 gram: this was then redissolved 

 and again precipitated and weighed as " pure " oxide ; the weight was 

 found to be 0*0284 gram. If we multiply the weight of crude lime, 

 0*0319 gram, by Dittmar's factor 0*91, we obtain 0*0290 gram as the 

 weight of " pure " lime. This amount only differs from that actually 

 found jby + 0*0006 gram, thus affording confirmatory evidence of the 

 correctness of the factor. 



The quantities of pure lime given below were determined by repre- 

 cipitation and repurification. The magnesia was precipitated by 

 * ' Challenger Keports,' "Physics and Chemistry," vol. 1. 



