ACADEMY OF SCIENCES] BIOGRAPHY 7 



personal contact which he always established with his students, together with his genial 

 disposition and sympathetic attitude, at once established a spirit of friendly cooperation on 

 the part of the student. Most of his students undoubtedly look back on these daily visits in 

 the laboratory as among their most pleasant and profitable experiences while at the university. 



When the work on osmotic pressure began Professor Morse was engaged in an extensive 

 investigation on permanganic acid. In the electrolytic method, which he devised for the 

 preparation of this substance, a solution of potassium permanganate was electrolyzed between 

 electrodes separated by a porous clay vessel. At times the pores of this vessel became filled 

 with finely divided manganese dioxide which was formed by the decomposition of the 

 permanganic acid. When in this condition the cells frequently showed slight osmotic activity. 

 This accidental formation of an osmotic cell furnished the idea that the artificial, semipermeable 

 membrane of Traube as used by Pfeffer could be deposited electrically and advantage taken of 

 the great driving force of the electric current to bring up a strong, continuous, semipermeable 

 membrane. Little difficulty was encountered in putting this idea into practice, and in 1901 

 a brief account of this ingenious method was published. 



Subsequent work showed that even such a perfect method for the formation of the 

 membrane could not give a perfect osmotic cell unless the porous clay vessel used for its 

 support was of the required texture. At first it was not believed that the matter of the porous 

 wall would be a difficult part of the problem of making an osmotic cell; it was thought that 

 the production of a suitable porous vessel could be left to the potter, with such instruction as 

 seemed necessary as to what was desired. After an experience of more than a year spent in 

 testing the products of several potteries, it was realized that if solved at all the problem must 

 be taken into the laboratory and a careful scientific study made of the conditions influencing 

 the texture of the product. The efforts of the potter were not, however, complete failures; a 

 few of the first lot of cells submitted, while not perfect, were quite good and served a most 

 valuable purpose, as I shall point out. Up to this time the direct measurement of osmotic 

 pressure of any magnitude was considered an experimental impossibility; but with the best of 

 these cells of the potter a number of measurements were made of the osmotic pressure of sucrose 

 solutions, thus demonstrating the possibilities of direct measurement. Unfortunately all of 

 these cells were broken in attempting to extend the work beyond the strength of the cells to 

 withstand pressure. These first cells of the potter served a second purpose also. By a micro^ 

 scopic study of sections of these cells the desired texture was ascertained, and this information 

 was of considerable aid in directing the course of the experiments when the production of a 

 suitable osmotic cell was made a laboratory problem. 



About two years were spent in continuous efforts to produce suitable osmotic cells. At 

 the end of that time it seemed that every possible precaution had been taken to secure success, 

 but failure was the result. But, with the knowledge that the potter had on one occasion suc- 

 ceeded quite well, efforts were continued until encouraging results were obtained; the first 

 stone was loosened and the wall was then easily breached. I shall not attempt to give any of 

 the details of these difficulties. What was constantly in mind during these disappointing years 

 was a perfect osmotic cell; this vision of perfection guided and sustained the efforts in the 

 laboratory until, as in the case of the potter of old, all that was foreseen was either found or 

 created. 



After having perfected a method for the deposition of the membrane and worked out in 

 detail the method for the production of a suitable cell, the remaining difficulties, which were 

 largely of a mechanical nature connected with assembling the various parts of the cell, were 

 rather easily overcome. And so, step by step, the obstacles were removed, until after a period 

 of about two years two good cells were finally produced in the laboratory and served to make the 

 first quantitative measurements, and the accumulation of data began. This brief statement will 

 give some idea of the difficult nature of the work. At the present time it requires about three 

 months to get an osmotic cell into measuring condition, and even then it must be given a con- 

 siderable period of rest between experiments, as it is disastrous to attempt to use a cell too 

 frequently. 



