ARTICLES 



231 



kept free from liquid the whole time by means of the compression 

 bulb. The tip is then carefully levelled by getting the cover of 

 the apparatus level (parallelism between the two having been 

 carefully attended to in the original assembling of the parts). 

 The liquid is now sucked slowly through the capillary, and a drop 

 of nearly the maximum size is allowed to form ; this drop is left 

 hanging for five minutes, so that any evaporation effects which 

 are going to occur may be completed : the drop is then allowed 

 to fall and twenty- nine other drops are collected, each being 

 allowed about one minute to form, and its shape being observed 

 during its formation by means of a lens to ensure that the drops 

 are " normal," great care being taken that the drops fall of 

 their own weight, by making the rate of formation very slow 

 towards the end of the formation of each drop. The liquid in 

 the capillary is then forced back, and the weighing bottle on the 

 supply side is removed ; any liquid adhering to the capillary is 

 taken up with filter-paper. The weighing bottle on the tip side 

 is dipped in cold water to condense any vapour, and the outside 

 having been dried, the bottle is disconnected, stoppered, and 

 weighed. The weight so obtained is that of a bottle together 

 with thirty drops of liquid and a certain amount of vapour. 

 The weighing bottle on the tip side is dried, and the parts of the 

 apparatus are assembled in the same order as before and the 

 whole is placed in the thermostat and left for the same time as 

 in the first part of the experiment ; a single drop is formed and 

 allowed to hang for five minutes ; five drops are then allowed to 

 fall, and the sixth is kept hanging at the end of the tip until the 

 total time is the same as in the first experiment ; the sixth drop 

 is then forced back into the supply vessel, and the weighing 

 bottle containing the five drops is removed with the same pre- 

 cautions as at first and is weighed. This gives the weight of 

 the bottle together with five drops and a certain amount of 

 vapour which, owing to the conditions of the experiment, cannot 

 be very different from that in the first experiment. Thus, if the 

 second weight is subtracted from the first, the weight of twenty- 

 five drops is obtained. The example now given shows results 

 obtained with benzene, M.W. 78 and t^ 288-5° C. 



The mean value of K from surface tension results being 2*115, 

 that of C becomes 2-1 15/2-291, and since T = Cmg, the surface 

 tension can be calculated ; in this way we get Tio = 29-20 



