1905.] Crystalloids and Colloids through Gelatine. 



323 



Examination for Neutral Red. — Table II. 



Original Fluid : 05 per cent, neutral red = (100) N.E. 



Filtrates: The 1st, 2nd and 3rd fractions showed (0*0), (2-3) and (0'04) 

 respectively. A sudden diminution in pressure from 100 to 20 atmospheres 

 caused a slight decrease in the value of the filtrate (0"03). On raising the 

 pressure once more to 100 atmospheres, the succeeding fractions gradually 

 increased in content up to (4*68) N.E. 



Eesidual Fluid : The colour intensity was much diminished and indicated 

 only (18-75) N.E. 



Conclusions. — The gelatine filter is slightly permeable at the beginning of 

 filtration to neutral red, but the permeability decreases, as in the case of 

 colloidal ferric hydrate, on continued nitration at constant pressure. 

 Diminution of pressure has the opposite effect to that obtained with sodium 

 chloride and ferric hydrate as the permeability tends to decrease. The filter 

 gradually becomes stained throughout and the permeability increases 

 correspondingly. 



Filtration of a Staining Crystalloid, Iodine in Potassium Iodide, through 

 11 per cent. Gelatine, under Varying Pressure. 



Iodine was chosen as a crystalloidal substance having the property of 

 staining gelatine, and potassium iodide was used as its solvent in water. 

 The interest of the experiment centred chiefly in the relative behaviour of the 

 two substances and the mutual influence they exert on each other during 

 filtration under varying pressure. 



Method. — A solution of 0'214 per cent, iodine in T54 per cent, potassium 

 iodide was filtered through 11 per cent, gelatine in 1*54 per cent, potassium 

 iodide. The content of the fractions of filtrate, etc., was determined by 

 titration with sodium thiosulphate, using starch as an indicator for the iodine 

 and with silver nitrate, using potassium chromate as indicator for the 

 potassium iodide. 



Examination for Iodine and Potassium Iodide. — Table II. 



Original Fluid : 0-214 per cent. I 2 = (100) I 2 . 1-54 per cent. KI = (100) KI. 



Filtrates: The 1st c.c. contained a considerable percentage of iodine (5) 

 and likewise of potassium iodide (68 - 8). On continued filtration at constant 

 pressure the iodine concentration rose steadily to (25) ; the iodide rose slightly 

 and then fell to (68'3). On suddenly diminishing the pressure from 100 to 

 15 atmospheres the iodine concentration diminished and the iodide increased. 

 On raising to 100 atmospheres the iodine rose, whereas the iodide rose and 

 then fell in concentration. Eemoviug the pressure for 12 hours the few drops 

 of liquid which percolated through contained no iodine and only (43) of 



