Knowledge. 



With wiiicli is incorporated Hard\vicl<e's Science Gossip, and tlie Illustrated Scientiiic News. 



A Monthly Record of Science. 



Conducted by Wilfred Mark Webb, l-.L.S., and E. S. Grew, M.A. 



JANUARY, 1911. 



A SIMPLE EXPERIMENT ON THE FORMATION OF 



DROPS OF LIOUID. 



Bv CHAKLi:s K. DARLING. A.R.C.Sc.L, F.I.C. 



When a suspended mass of H(iui(l attains a definite 

 size it becomes too heav\' to be sustained bv the 

 adhesion of the li(]uid to the surface from which it 

 hangs, and, consequentl\", a i)orti(>n breaks awaw 

 resulting in the formation of a spherical droj). 

 WHien the liquid hangs in air. as in the case of water 

 on the end of a leaky tap, the drop breaks away ttio 

 (]uickly to jiermit the process of separation to be 

 obser\ed by the unaided eve. In order to study 

 the changes in outline undergone b}- the suspended 

 liquid, instantaneous photograph\' and rapidh- 

 intermittent light have been emplo\ed, and ha\'e 

 succeeded in disclosing the beautiful transition 



inches in (Hanieter, is tilled with water to the height 

 of ahum four and a-half incites, and seventy or eighty 

 cubic centimetres of commercial aniline are added, 

 which will sink to the bottom of the vessel. The 

 temperature of tlie beaker and its contents is now 

 raised to 75'' or 80° C. b)' means of a burner, when 

 it will be observed that the aniline will rise to the 

 surface of the water, from which it will hang in a 

 mass of curved outline. Almost immediatel}- the 

 suspended aniline commences to alter in shape ; 

 and gradually a large (h'op. an iiieh or more in 

 diameter, detaches itself from the mass and falls 

 through the water. The formation of this droi) 



Tirr 



3 4 



The forniation of a drop of aniline. 



shapes which accompan\' the detachment of the 

 drop. Either of these methods of observation, how- 

 ever, demands the use of elaborate instruments, and 

 it is here proposed to describe an experiment of the 

 simplest description, which not only enables the 

 process to be followed easily by the eye, but is unique 

 in the respect that the formation of the drops is 

 automatic and continuous. It was arrived at by the 

 author as the result of a comparative stud\- of the 

 physical properties of water and other liquids of 

 approximatelv equal densitw 



A glass beaker, about six inches high and four 



takes place so slowly, owing to the aniline being 

 buoved up bv the water beneath, that all the changes 

 of shape associated with the process may be observed 

 distinctlv. The appearance presented is well shown 

 in the accompanying photographs, taken by Mr. B. 

 Abel, of the Ci"t>- and Guilds Technical College, 

 Finsburv, with an ordinary hand camera. In 

 No. 1 the formation is commencing ; No. 2 repre- 

 sents the stage just preceding the formation of the 

 neck ; in No. 3 the neck has formed, and in No. 4 

 the drop has just broken away : No. 5 shows the 

 flattening of the drop due to the shock of breakage, 



