122 



KNOWLEDGE. 



April, 1913. 



Figure 118. 



explained. Orthotoluidine, for example, does not 

 lend itself to these formations : and in the case of 

 aniline a vessel of five centimetres in diameter is 

 required, and even then it is difficult to prevent the 

 column from sticking to the side, and so spoiling the 



shape. Iso-butyl benzoate, 

 as purchased, varies con- 

 siderably; the first sample 

 procured by the writer 

 behaved ideally, as in 

 Figure 117, but three 

 other specimens since 

 obtained have entirely 

 failed to produce satis- 

 factory columns. Hence 

 ^Figure 117 '* * s recommended, when 



it is desired to produce a 

 column with certainty, to 

 use aceto-acetic ether, 

 which has given uniformly 

 successful results. 



The Movements of 



Liquid Globules on 



a Water Surface. 



Investigations of move- 

 ments on the surface of 

 water have hitherto been 

 restricted to the rotation 

 of camphor and a few other solids, and to the forma- 

 tion of films of oil, which spread across the surface 

 rapidly in all directions from the spot on which the 

 oil is placed. Whilst experimenting with aniline 

 and orthotoluidine with a view to the formation 

 of drops, the writer observed that the globules which 

 floated on the surface of the water showed move- 

 ments of a type not previously recorded, and for 

 which no satisfactory explanation has yet been 

 given. So far no photographs have been secured 

 which give an idea of the nature of the movements 

 in question, and hence it will be necessary to resort 

 to drawings in order that an idea may be formed as 

 to the nature of the phenomena. The accompanying 

 illustrations are the work of Mr. W. Narbeth, one of 

 the writer's students, and correctly represent certain 

 stages ; but to observe the movements to full advan- 

 tage it is necessary to perform the experiments. In 

 order to produce surface globules, a dish, ten centi- 

 metres or more in diameter, is taken — a photographic 

 dish answers well — and rinsed several times with 

 tap-water before it is filled. One or two drops of the 

 liquid under trial are then allowed to trickle down 

 the side of the vessel on to the water, when globules, 

 sooner or later, will form. A dropping bottle or fine 

 pipette will be found convenient for regulating the 

 quantity of liquid, which, if too large, may obscure 

 the movements. 



When a drop of red-coloured, commercial aniline 

 is thus floated on clean water, globules are formed 

 which display movements best expressed bv the word 

 " twitching." What actually occurs is that the 



globule is stretched at first, but afterwards recoils, 

 forming a globule of less diameter and greater depth. 

 This alternate expansion and contraction is accom- 

 panied by the detachment of small globules from the 

 rim, which becomes indented as shown in the largest 

 globule depicted in Figure 121, the small globules 

 being formed from the protuberances. After shrink- 

 ing, the appearance presented is indicated by the 

 second largest globule in Figure 121, which is shown 

 surrounded at a distance by the small, detached 

 globules. Finally, owing to continued partition at 

 the rim, the diameter diminishes until, at a certain 

 point, the movement ceases, leaving a number of 

 small globules floating tranquilly on the water. If 

 only a minute quantity of aniline be used, the 

 globules may disappear entirely by spreading over 

 the surface or by solution. 



The next movement to be described is even more 

 remarkable, and was first obtained by the author 

 with orthotoluidine, but was only shown to perfec- 

 tion by one sample. Other quantities of the liquid 

 since obtained have failed for some reason to produce 

 equally good results ; but the same movement is 

 exhibited by the liquid xylidine 1-3-4. The globules 

 formed when one or two drops of this liquid are 

 allowed to run on the surface of water are endowed 

 with remarkable activity. Simultaneously, all the 

 globules above a certain size become indented on 

 one side only, so as to resemble a kidney in shape, 



when each is projected 

 violently across the surface 

 of the water. Some of the 

 forms taken by the 

 globules are shown in 

 Figure 122, in which it 

 will be seen that in the 

 process fragments are 

 broken off the larger ones ; 

 and sometimes the in- 

 dentation spreads to the 

 opposite side and cuts 

 the globule into two. A 

 period of repose then 



Figure 119. 



follows, in which the 

 globules all possess a 

 circular outline ; when 

 suddenly, moved by a 

 common impulse, all the 

 larger globules again 

 assume the kidney shape 

 and dart across the sur- 

 face. This continues 

 until a number of small 

 globules are left quietly 

 floating on the surface ; or 

 the whole may disappear 

 by spreading and solution. 

 Sometimes the movements will continue, with increas- 

 ing sluggishness, for an hour or more. The direction 

 of motion across the surface is always away from the 

 indentation, as if the globules were pushed by the 



Figure 120. 



^Figures 117-120. A column of iso-butyl benzoate, stretched by adding water until breakage occurs. Four stages. 



