142 SMITH AND EXNER — ATOMIC WEIGHT OF TUNGSTEN. [April 7, 



thus reached a temperature of nearly 350° C. These burners were 

 then extinguished, while those immediately beneath the boat were 

 lighted, the flames being small. The tube to a length of eight 

 inches beyond the boat was also heated. In a very short time the 

 reaction began, noticeable at first in the yellow vapors which con- 

 densed in the colder part of the tube, beyond the furnace, to the 

 light brown oxychloride. This did not continue more than two 

 minutes, when copious reddish-brown vapors appeared and con- 

 densed beyond the lighted burners to brilliant blue-black needles. 

 The formation is very rapid. The utmost vigilance is constantly 

 required to the very conclusion of the experiment. In two hours 

 twenty grams of metal may be fully converted into hexachloride. 

 That portion of the combustion tube at which the hexachloride 

 condenses should be kept just hot enough to cause the traces of 

 oxychloride to pass beyond the hexachloride. This can be readily 

 adjusted after a little experience. When v/orking with large 

 amounts the deposits of the hexachloride may obstruct the tube. 

 In that event manipulate a lamp flame v/ith the hand beneath the 

 chloride until it is partially melted. This converts it into a com- 

 pact solid, requiring less space. Melting and resublimation of the 

 chloride removes every trace of oxychloride. Two sublimations 

 are sufficient for the purpose. The tube can then be sealed off at 

 the contracted points. Perfectly pure hexachloride has a beautiful, 

 brilliant steel-blue color. It can be readily transferred to clean, 

 dry weighing bottles and preserved in them. It has marked 

 stability. There is no perceptible action on bringing the chloride 

 into water at the ordinary temperature even after considerable 

 time. On the application of heat the decomposition does not begin 

 until the temperature of the water reaches 60°. The specific 

 gravity of the hexachloride, taken in water at the ordinary tem- 

 perature, equaled 3.518. After all the weighings were made the 

 water employed for the purpose was tested with litmus ; it gave the 

 very faintest acid reaction. Having obtained in the above man- 

 ner large quantities of the hexachloride, it was decided to change it 

 to trioxide and thus arrive at the atomic weight of the metal. 

 Roscoe had determined the chlorine in this compound. His results 

 were not especially concordant. Perhaps this was due to the 

 involved method or to the presence of traces of oxychloride* 

 However, our thought was to adopt the simplest available course, 

 hence we aimed to convert the chloride into oxide. Roscoe has 



