318 



Mr. J. A. Craw. On the Filtration of [Dec. 1, 



acid greatly diminishes the surface tension of saline against air, and the 

 possibility of a change in the surface forces between saline and gelatine formed 

 a second point of interest, which is discussed towards the end of this paper. 



Method. — A solution of 081 per cent. NaCl containing 4"8 per cent, 

 butyric acid was pressed through 9 per cent, gelatine in 0"81 per cent. NaCl 

 at 100 atmospheres. The content of the fractions of filtrate, etc., in NaCl 

 was determined as before, and the butyric acid was estimated by titration 

 with standard sodium hydrate, using phenol-phthalein as indicator. The 

 hsemolytic powers of the various fluids were also determined by the time 

 taken for 1 c.c. of the fractions to hsemolyse completely 2 c.c. of a 2 - 5 per 

 cent, suspension of guinea-pig's corpuscles in - 8 per cent. NaCl at 16° C. 



Examination for Sodium Chloride. — Experiment No. 3, Table I. The 

 redistribution of salt was qualitatively similar to that which had been 

 obtained in the absence of butyric acid. The amount passing into the filtrate 

 was, however, smaller. 



Examination for Butyric Acid and Hemolytic Power. — Original : 4 - 8 per 

 cent, butyric acid = (100) HBu. Hsemolytic time = 8 minutes. 



Filtrates : The 1st and 2nd fractions contained (0 - 2) and (5"8) HBu 

 respectively. The 1st fraction agglutinated the test blood strongly, and the 

 2nd hsemolysed completely in 50 minutes. The 8th to the 11th fractions 

 contained (90 - 6) HBu, and the hsemolytic time was 12 minutes. 



Eesidual Fluid: Concentration (125) HBu. Hemolytic time, 5 minutes. 



Conclusions. — Butyric acid is retained by gelatine to a considerable extent. 

 The gelatine appears to retain more sodium chloride in the presence of 

 butyric acid. 



Filtration of Sodium Chloride through 9 per cent. Formalised Gelatine. 



It seemed probable, from the marked change which takes place in gelatine 

 on being exposed to formic aldehyde, that such gelatine would show a different 

 permeability to that already found for ordinary gelatine. On the other hand, 

 the possibility of investigating physiological fluids in an apparatus which 

 could be thoroughly and easily sterilised by means of " formalin " might 

 recommend the use of formalised gelatine filters. 



Method. — A filter containing 9 per cent, gelatine in - 8 per cent. NaCl was 

 fitted into the filter case, and the latter filled with a solution of 0"8 per cent 

 NaCl containing 10 per cent, of commercial " Formalin." A few cubic centi- 

 metres of fluid were pressed through, and the remainder allowed to stand in 

 the filter case overnight. The solution was then removed, and, after about 

 12 hours, 100 c.c. of - 88 per cent. NaCl were placed in the filter case, and 

 pressed through in fractions of 4 to 5 c.c. 



