of a Liquid Mass without Weight. 



453 



case of those liquids of the first and third categories in which 

 the superficial viscosity does not greatly exceed that of water, 

 we may adopt as approximate relative values the ratios between 

 the times occupied by the movement of the magnetic needle at 

 the surface and in the interior; a small correction, however, 

 must be applied to this ratio in the case of liquids like glycerine, 

 in which the internal viscosity is very great. I have therefore 

 calculated these ratios ; then representing the superficial visco- 

 sity of water by 100, I have expressed those of the other liquids 

 in the same units; and, lastly, I have divided the numbers so 

 obtained by the respective tensions of the films, and have thus 

 formed the two Tables which follow : — 



First Category. 



Liquids. 



Superficial 

 viscosity. 



Water 10000 



Price's glycerine I 60-42 



Carbonate of sodium (saturated 1 oi.ii 



solution). ) y114 



Nitrate of potassium (saturated 1 nc.oz 



solution) ) ybJO 



Chloride of calcium (saturated 1 on.** 



solution) .. j 90b2 



Tension of 

 films. 



14-60 

 800 



8-56 

 11-22 



11-06 



Ratio of superfi- 

 cial viscosity 

 to tension. 



6-85 

 755 



10-65 

 8-59 

 8-19 



Third Category. 



Solution of Marseilles soap,l : 40 

 , soft household soap,l : 30 

 , potash resin-soap ... . 



saponine 1 : 100 

 albumen 



94-79 



5-64 



96-95 



6-44 



84-89 



7-68 



Not determined, 



1 f 



but extremely 



r 8 ' 74 



great. 



J I 



Idem. 



11-42 



16-81 

 14-96 

 1105 



Not determined, 



but extremely 



great. 



Idem. 



It will be seeu, on looking at these Tables, that the ratios of 

 superficial viscosity to tension are all greater for the liquids of 

 the third category (that is to say, for those which yield bubbles 

 and a copious froth) than for those of the first category, and 

 moreover that, with a single exception, the difference is con- 

 siderable. 



In the second place, of the liquids in the first Table, that one 

 for which the ratio of these two elements has the highest value 

 (namely solution of carbonate of sodium) is precisely the one 

 which, when shaken in a flask, yields the most perceptible froth ; 

 we may therefore suppose that if a saturated solution of carbonate 

 of sodium is incapable of forming bubbles, it is not so far from 

 having that property as the four other liquids. 



