558 



a <j;Teat number of pieces. It is extremely diffieuU, again to eliminate 

 such transported air-biibbles, even in repeating the above mentioned 

 way of rising and falling of the liquid in the capillary tube for a 

 number of times. Almost quite impossible is the elimination of the 

 air, if the wall of the tube moreover is attacked by the molten salt, 

 — this wall becoming more or less rough by it: the nir-bubbles 

 will then persist in sticking to the narrow canal. 



Moreover the microscopical control of the glass-tubes proved 

 doubtlessly that the walls of it were attacked by the molten salt 

 almost always seriously to a more or less extent; this fact, in con- 

 nection with the just mentioned difficulties caused by the not 

 removable air-bubbles and the impossibility to determine sufliciently 

 the exact situation of the surface of the liquid in 2', were the chief 

 causes why these tentatives finally had to be stopped. In some cases, 

 e.g. in that of sodiumchronuite, we could obtain rather reliable data ; 

 but e.g. with lithiumsalts, which will always attack the glass in a 

 high degree, and just so in the case of silvernitrate, only very un- 

 trustworthy numbers could be obtained. It appeared moreover to be 

 very difficult, to keep the temperature constant along the full length 

 of the capillary tube; this can soon be controlled by means of a 

 set of very small thermometers, placed within B at several distances 

 from the bottom. 



§ 4. After this experience we thought it adviceable to abandon 

 the said method completely. All numbers- here given therefore are 

 collected after the method formerly described by us in detail'); 

 they relate to the purest salts. B'or the details of these experiments 

 the reader is referred to Comm. I of this series. 



§ 5. Measurements of moUen Ahali-halogenides. 



This series includes the following salts : The Fluorides and Chlorides 

 of Lithium, Sodium, Potassium, Rubidium and Caesium, and the 

 Bromides and Iodides of Sodium, Potassium, Rubidium and Caesium. 

 The preparation of the anhydrous l)roniide and iodide of lithium 

 gave hitherto no good results, because of the hydrolysis caused by 

 heating the crystallized, hydrated salts. 



1) F. M. Jaeger, loco cit. 385—348. 



