A COLLODION DIFFUSIOX CELL FOR USE I S DIALYSIS. BY T. R. BRIGGS
Collodion membranes for use in dialysis have been described and studied by Bigelow and Gemberling, who, having reviewed the literature very completely, recommend the preparation of collodion sacs for dialysis by n’ovy’s method. Recently, however, I found myself called upon to separate several colloid and semi-colloid dyes by the diffusion method and, on attempting to prepare collodion sacs according to Novy’s directions, found t h a t the operation required considerable practice before it could be carried out successfully. Parchment diffusion thimbles were not conveniently a t hand, so the following procedure was adopted : A large Soxhlet extraction cartridge (80 x 2 j mm) composed of rather thick filter paper was filled with a collodion solution (Kahlbaum’s Ph.G.V), and emptied again as soon as the solution had completely impregnated the pores of the paper. The cartridge was allowed to “dry” for a few moments until the collodion had set; thereupon, the filling and emptying process was repeated. In this way three coats of collodion were applied t o the interior of the cartridge. Baranetzky’ has observed that a collodion membrane wlaich has Completely dried o u t is practically impervious to water, while if the freshly prepared membrane be placed into water before the alcohol present has completely evaporated, the result is a film of pyroxylin quite permeable t o water. Accordingly, the cartridge prepared as described cannot be allowed to dry out in the air, but must be immersed in water and kept under water until used. After the third coat of collodion has been applied, the cartridge is dried in a current of air until practically all the ether of the mixed solvent is removed, about ten minutes being required for this to occur. Jour. Am. Chem. SOC.,29, 1576 (1907). Pogg. Ann 147,2 1 9 ( 1 8 7 2 ) .
T . R.Briggs
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Thereupon, on immersing the cartridge in distilled water, the alcohol retained in the pores of the collodion is displaced quickly and completely by diffusion, and the cell is ready for use. The diffusion cells were tested qualitatively for imperfections and leaks in the collodion membrane by carrying out diffusion tests, as follows. A cartridge was filled to within half an inch of the top with a mixed solution of sodium chloride and congo red, a dye which forms non-diffusing and distinctly colloidal so1utions.l On partially immersing the cell in distilled water it was found that the sodium chloride dialyzed out while not a trace of congo red appeared in the diffusate; since the liquid stood higher inside the cell than outside, any leak would have been detected a t once by the appearance of the red dye in the outer liquid. Comparative tests were next made of two parchment and two collodion diffusion cells by determining the amount of sodium chloride diffusing through the walls in twenty-four hours under carefully controlled and very nearly identical conditions. Four cells of practically the same dimensions were employed, partly filled with 2 0 cc of standard (approximately N IO) sodium chloride solution plus 25 cc of distilled water and placed in running tap water in a specially designed apparatus. After twenty-four hours the amount of salt left behind in each thimble was determined by titration with standard silver nitrate. The results follow. TABLEI-COMPARATIVE TESTS Parchment diffusion thimbles previously well soaked in mater Collodion extraction thimbles (C. S. 81 S. No. 603) ~~~~
.___
~~
~
Parchment cells
I
_.
No
I
No z
I
Collodion cells - _ _ No I So z
Time of test (hrs.) 23 23 j 23 23 Volume of solution (cc) 45 45 45 45 NaCl originally present (g) o 118 o 1181 o 118 o 118 NaCl removed by diffusion (g) o 092 o 092, o I I Z o 113 Percent NaCl removed by diffusion 77 g 77 g 1 94 g 94 8 ~~
Freundlich Kapillarchemie, 564 (1909).
A Collodion Dijusion Cell j o r I-se in Dialysis
379
The results of the test were very favorable t o the collodion membranes as the data indicate. The only apparent disadvantage possessed by the collodion cells is a tendency to overflow because of water entering by osmosis, a phenomenon which is absent in the case of parchment. Bigelow has observed the same behavior. I have already called attention t o the fact that collodion membranes lose their permeability if they are allowed to dry completely. This is due, without doubt, to irreversible changes leading to the collapse of the pores in the material. It would seem, according t o this theory, if one were to add t o the original collodion solution some tzowcolatile liquid (or solid) soluble both in water and the ether-alcohol pyroxylin solvent, that under these circumstances the collodion film might be dried in the air and still retain the property of being permeable to water, on replacement of the non-volatile liquid in the pores by immersion in water. Experiment confirmed this most satisfactorily. Glycerine dissolves readily in collodion solution and was employed in the following experiments : Three different collodion solutions were used t o prepare the diffusion shells according t o the method just described: Solution I contained no glycerine; No. 2 contained 4 percent glycerine by volume; Nos. 3 and 4 contained 6 and I O percent, respectively. Soxhlet thimbles were coated on the inside with three layers of each solution and then dried in the air, thereupon the removal of volatile solvent was completed by heating in a water-oven for several hours. After several weeks had elapsed, the usual comparative tests were made, each cartridge being soaked in water t o remove the glycerine from the membrane, before the tests were begun. The data follow.
TABLE 11-COMPARATIVE TESTS ( a ) Cartridge with three coats of collodion KO. I . air. Weight of collodion when dry: 0.430 g. Percent moved by diffusion in 24 hrs. : 4 j 8. ( b ) Cartridge with three coats of collodion S o . 2 . air. Weight of collodion when dry: o j8o g. Percent moved by diffusion in 23 hrs.: 7j.
Dried in NaCl reDried in NaCl re-
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T . R. Briggs
(c) Cartridge with three coats of collodion S o . 3. Dried in air. 11-eight of collodion film when dry: o 886 g. Percent SaCl removed by diffusion in 24 hrs. 89 2 . (d’) Cartridge Jrith three coats of collodion KO.4. Dried in air. Weight of collodion when dry: I 089 g. Percent NaCl removed by diffusion in 24 hrs.. 58 1. ( e ) Parchment thimble. Percent KaC1 removed by diffusion in 24 hrs. 83 6. ( f ) Collodion thimble made according to S o v y ’ s method without use of filter-paper Soxhlet thimble. Percent SaCl removed by diffusion in 2 1 hrs.: 99 6.
These data show that the amount of glycerine in the dried collodion membranes varied up to approximately 60 percent by weight, and that the permeability of the cells increased as the glycerine content rose to about j o percent, after which it remained practically constant. The collodion cells are more efficient than parchment thimbles, though they are less so than the beautiful transparent sacs formed directly from collodion. The ease with which the cartridges are prepared and their durabilitl- more than makes up for the lower efficiency. Several cartridges prepared with glycerine have been kept for more than eight months without losing their effectiveness as dialyzing cells. The results of this paper may be summarized as follows: I . Collodionized Soxhlet extraction thimbles have been suggested as con\-enient cells for dialysis. 2 . The construction of such cells has been described and comparisons have been made with parchment diffusion shells. 3. By the addition of a small amount of glycerine to the collodion solution the cells may be prepared so that they may be dried completely without losing their permeability to water. Such cells may be kept for a long time before using. 4. The new form of collodion diffusion cell is more efficient than the ordinary type of parchment thimble, but is less efficient than collodion sacs prepared by Novy’s method. Torcester Pol3techizzc I7zstzfz~te Cornell CizzzersrtJ
