ABSORPTION OF WATER 



57 



54. Demonstration of Osmosis. — The contents of a 

 hen's egg are enclosed by a porous membrane closely ap- 

 pressed to the inside of the shell, except at the large end 

 of the egg. At this end the shell, as may readily be seen, 

 is more porous than elsewhere, so that air readily enters, 

 pressing the membrane in, and forming an air-chamber 

 between it and the shell. With a sharp-pointed knife 

 the shell may here be punctured, and with the aid of small 

 scissors, removed so as to make an opening from J>-^ to 

 ■^4 inch in diameter. The greatest care must be taken not 



Fig. 44. — Experiment with an egg to demonstrate osmosis. A, at the 

 beginning; B, about one hour later; w, water surface; s, support; m, egg- 

 membrane. 



to puncture the membrane, which at this region, lies 

 concave (Fig. 44). 



The contents of the egg are the yolk, the "white" 

 (albumen) , and an aqueous solution of various salts, which 

 permeates the yolk and the "white." If, now, the egg 

 is placed upright in a glass of water, so as to be completely 

 covered by the water, we shall have realized the condi- 

 tions for tsmosis, the two liquids being the water outside 

 and the aqueous solution inside the egg. Within a short 

 time the less dense water will have passed through the 

 membrane so much more rapidly than the dissolved salts 



