383 
Experience shows, that in most cases the third figure could still be 
considered to be certain, — which accuracy is wholly sufficient for 
our purpose. 
2. Of course neither a pycnometer nor a volumeter could be 
used in cases, where the organic substances had a too high 
melting-point; and a fortiori this was the case with the inorganic 
salts melting at extremely high temperatures. In these cases the only 
way was to use a Aydrostatical method, in which a sinker is used, 
which is described: in detail further-on. Only in such cases, where 
the substance investigated appeared to be so volatile, as to give a 
rapid sublimation against the colder parts of the suspension-wire, 
it was not possible to apply this method. In such, — happily only 
rare cases, — the determination of the specific weight must be 
given up completely; the same was the case, if the viscosity of the 
molten mass or its surface-energy surpassed certain limits. 
The apparatus used in the determinations of the specific gravities 
of such molten salts, up to temperatures of 1500° C, had finally, 
after many alterations and varied constructions, the here described 
form (fig. 2). 
To one of the scales of a sensitive analytical balance a platinum- 
Fig. 2. 
wire as thin as possible, /’ (about 80 em. long) was fixed by means 
of a small ringlet. For measurements from 4200° to 1600° C., this 
wire has to be at least 0.8 mm. thiek, because it would break 
