426 



Tlie bcliaviour of siieli extreiiiely viscous lifjuids with respect to 

 the <2,as-biib!>les pi-odiiced in Ihem, is very variable and often very 

 peculiar : in this case the bubbles are hardly loosened from the 

 capillary tube, in that case one observes a periodic increase and 

 decrease of tlie gas-pressure, without a bursting of the bubbles 

 occurring ; in another case a very large bubble is produced, which 

 suddenly explodes into a great number of very small bid^bles ; but 

 in no case a maximum pressure can be measured, which is really 

 //«dependent of the speed of the gas-flow, proving that it corresponds 

 to a real state of equilibrium of the gas-bubble. And this last men- 

 tioned fact is so characteristic for all our other measurements : 

 loithin rather tuide limits one can vary the speed of nitrogen-jl.ow, when 

 working nnth ordinary liquids, rvithout a measurable change in the 

 determined pressure H being observed. On the contrary we studied 

 a long series of very thin liquids : e.g. ethylalcoJiol, diethylether, ethyl- 

 formiate, ethyJchloroformiate, acetone, m ethyl propy ketone , chloroform, 

 etc., cooled to — 80° C, which notwithstanding the low temperatures 

 gave xery reliable values of //; the occasional fact that the temperature 

 is so low, can therefore neither be considered of high importance 

 for the abnormally high values of •/ and ft observed. However it 

 must be said in this connection, that Eötvös' relation can no longer 

 be considered as valid at temperatures, lower than about half the 

 absolute critical temperature of the studied liquids. 



In this connection it is not superfluous to remark, that with liquids 

 whose volatility is very great, and which therefore possess at higher 

 temperatures a very considerable vapour-tension, there is often some 

 difficulty in obtaining reliable values for H, this maximum-pressure 

 being apparently somewhat increased. However the right value can 

 be deduced in such cases by often repeating the adjustment of the 

 capillary tube, uniil a really reproducible \'alue will be found. The 

 influence of these abnormally high vapour-tensions cannot be of 

 essential signideance, if the measurements are controlled accurately 

 and often careful!}^ repeated. 



All arguments taken together, we think it really very improbable, 

 that the changes in viscosity of the studied liquids could l)e argued 

 as the chief cause of the observed curvature of the x-^ or ji-^curves. 

 But in cases of abnormally great values of the viscosity, the deter- 

 mination seems doubtlessly no longer possible after this method in 

 any exact way; however with liquids, whose viscosity comes e.g. 

 very near to that of glycerine, or is even somewhat greater, such 

 measurements are already quite reliable if only the formation 

 of the gasbubbles takes place extremely slowly: in this way for 



