ENDOSMOTIC EQUIVALENTS. 



491 



Fig. a 



The apparatus used was an endosmometer, made on the 

 same principle as the instrument constructed by Dutrochet, 

 but so modified as to obviate certain elements of inaccuracy 

 in comparative experiments. The reservoir, or bulb, was three 

 inches in diameter at the lowest portion, to which the mem- 

 brane was applied, and its capacity was five or six ounces. 

 To this was attached a vertical tube, six inches in length, 

 with a calibre of about 

 three-tenths of an inch, 

 or one-tenth the diameter 

 of the bulb. The mem- 

 brane used was the blad- 

 der of the ox, with the 

 muscular coat removed. 

 Sometimes the membrane 

 was doubled. To avoid 

 the stretching of the mem- 

 brane by pressure of li- 

 quid in the tube, it was 

 supported by a slightly 

 concave perforated zinc 

 plate, carefully varnished, 

 to prevent its being acted 

 upon by the solutions, and 

 resting on a tripod. This 

 apparatus was filled with 

 the solution up to a point 

 marked zero on the verti- 

 cal tube, and then placed 

 in a jar containing about 

 sixtv ounces of distilled 



, n ^ . -, Instrument used by Graham for determining os- 



Water, tile SUriaCe OI Which motic equivalents. (Elements of Inorganic 

 _ ,, , , Chemistry, Philadelphia, 1858, p. 749.) 



was careiully brought to 



the level of the liquid in the tube. 1 In most of the com- 



GRAHAM, On Osmotic Force. Philosophical Transactions, London, 1854, p. 



185. 



