THE ATOMIC WEIGHT OF TUNGSTEN. 7 



of metallic tungsten, the first A had not been specially freed from molybdenum, 

 the second B was a portion of III. The determinations were made in a 

 specific gravity bottle of 10 c.c. capacity. The bottle was weighed empty, and 

 full of distilled water which had been boiled to expel air. The bottle was 

 then dried and weighed again, then some tungsten was introduced, and another 

 weighing was made. The metal was afterwards covered with water, and the 

 bottle placed under an air-pump, in order to extract the air enclosed in the 

 powder. The bottle was then filled with water, and a weighing again made, 

 and as the water evaporated slowly, but perceptibly, weighings were taken 

 when the meniscus in the capillary touched two fixed marks scratched on the 

 stopper. How nearly the readings agreed, is shown in the table below. 



Specimen. 



Wt. tungsten. 



Reading. 



Weight water 

 displaced. 



Specific gravity. 



A 

 B 



1-0353 

 ■7187 



Upper mark 

 Lower mark 

 Upper mark 

 Lower mark 



•0566 

 ■0566 

 •0382 

 •0383 



18-249 

 18-249 

 18-772 

 18-765 



Most reliance should be placed upon the result obtained with B, because of 

 the assured purity of the metal, and because a first trial would be liable to 

 experimental errors. All such errors tend to give a low specific gravity. 



It was not thought necessary to make another determination, because the 

 number agrees so well with those obtained by the best authorities. The 

 highest determination is that given by Roscoe, viz., 1913; the majority of 

 experimenters give figures lying between 18 and 19, while a number so low as 

 16-54 has been obtained. The density seems to depend upon the method of 

 preparing the metal. 



My work has been confirmatory of the commonly accepted atomic weight 

 and specific gravity of tungsten ; its chief value lies in the fact that the subject 

 was attacked in a way so far as I know not hitherto attempted, and the corro- 

 borative evidence is therefore all the more trustworthy. 



My thanks are due to Prof. Crum Brown and Dr Gibson for valuable 

 suggestions and kindly assistance. 



