2 L. H. Bori^ströiii. (LVII 



ature of the sample at the moment it melts. The heatiiig is 

 as a rule performed in an electric furnace, which may be 

 regarded as an airbath, in which the pyrometer and the 

 sample are placed near one another. Only if the heating 

 is very slow it is possible to attain a sufficient uniformity 

 of temperature, which alone can render this method ac- 

 ciirate. 



With the object of evading the disadvantages of the cited 

 methods the author has employed a procedure, which is 

 analogous to the one commonly used in the practice of 

 organic chemistry. A very small quantity of the mineral 

 was inserted into a glasscapillary and heated in a liquid, the 

 temperature of which was observed. O s t w a 1 d and 

 Luther ^) have estimatcd the accuracy of this method 

 in the laboratories of organic chemistry to 0,2° — 0,5°. The 

 superiority of the licjuid bath över the airbath is illustrated 

 by the difference in the length of time required by a mer- 

 curythermometer to adjust itself to the temperature of the 

 bath. While thus the difference in temperature between a 

 thermometer and a liquid disappears in 3 to 10 seconds, if 

 the bath is stirred, and in 15 to 30 seconds, if the stirring is 

 omitted, 3 to 10 minutes are necessary in circulating vapours 

 and 15 to 30 minutes in a stagnating gas 2). As bathliquids 

 the following molten salts have bcen used by the author. 

 They are all at the temperatures of the experiments colour- 

 less, clear and very fluid: 



from (S10° upwards purc NaCl 



between 630° and 850° 7 parts Na^SO^ and 3 parts NaCl 



» 380° » 650° 3 » KCl » 1 part LiCl. 



» 220° » 450° 55 » NaNO^ » 45 parts /vNOg 



The temperature was taken with a P/-P/i?/i-thermo- 

 element and the solder was introduced into the bath without 



') o s t w a 1 d-F. u t II e r. Physiko-clicniische Messungen 3:d edition. 

 Leipzig. 1910 p. 222. 



2) O s t w a 1 d-L II t h e r 1. c. p. 9.*?. 



