LIESEGANG'S LINES. 

 'Plate 9). 



By Prof. W. A. D. Rudge, M.A. 



The author, in the course of his investigations on the action of 

 Radium and other salts on gelatin, observed that in certain cases 

 when a particle of a solid salt was placed in contact with some 

 solidified gelatin, impregnated with another salt, a concentric 

 growth took place, forming a series of well-defined rings. It was 

 pointed out to him that these rings had been observed before by 

 Liesegang, and the theory worked out by Ostwald. Morse and 

 Pierce had also experimented with them and had shown that the 



% 



radius* of the ring could be deduced by aid of the formula — = = K 



when :x; = radius of the ring, and i— the time elapsing before it began 

 to form, and K a constant. The constant varied with the tempera- 

 i ure. 



The materials which give the best results are potassium 

 chromate in the gelatin, with silver nitrate as the solid salt. The 

 jelly used contained 3% of gelatin and 1% of potassium chromate. 

 Fig. I. shows the general appearance of a set of lines under a mag- 

 nification of 30. 



The present contribution to the know^ledge of this subject consists 

 in the investigation of the remarkable figures obtained when two 

 or more sets of lines are allowed to grow close to each other. It 

 occurred to the author that as the figures resemble so much the 

 growth of a set of waves round a central source of disturbance, 

 it might be possible to get some interference effects, if two sets 

 were formed in proximity to each other. Some gelatin containing 

 chromate was allowed to solidify on a glass plate — then three small 

 specks of silver nitrate were placed close together on the gelatin^ 

 and the development watched under the microscope. The result 

 is seen in Fig. II. Each particle gave rise to a series of rings, 

 which were concentric with the particles until the growths neared 

 each other, when the rings from the adjacent sets were seen to 

 combine, somewhat as two sets of waves might combine, leaving 

 a space where no lines are seen, and in other places uniting together 

 to form a common front. Fig. III. 



The remarkable effect becomes evident that the lines from one 

 set never cross those due to another, but one set will grow round 

 another, the lines from one of the larger growths opening out when 

 nearing those from a smaller one, as though some sort of attraction 

 existed to deviate the lines from their normal course, and some 

 force acted to bring them back again into their normal position. 

 Fig. IV. This apparent attraction between the lines is one which 

 takes place at considerable distances as seen in Fig. V., where the 

 distance between the sets of lines is so great that the systems 

 never meet, but get the tendency of the lines from one centre of 

 growth to meet those from another centre is most clearly seen. 

 Fig. VI. shows the attraction between four sets. 



* "Physical Review," XVII., 129-150. 



