24 STUDIES IN PHYSIOLOGY. 



What effects are produced when a solution of potassic ferro- 

 cyanide is shaken up with a solution of copper chloride? 



The pellicle precipitates can be further examined as directed on 

 page 226. Calcic chloride and sodic carbonate can be employed 

 in the examination instead of the substances there mentioned. 



IV. PFEFFER'S ARTIFICIAL CELL. 



Repeat Pfeffer's experiments (page 227), with all the precau- 

 tions there advised. 



In every case where a manometer, or pressure-gauge, is to be 

 used, corrections must be made for temperature and for baro- 

 metric pressure according to the directions given in such works 

 as Bunsen's " Gasornetr}-." 



V. ABSORPTION OF WATER. 



Moisten one side of a perfectly flat, thin piece of hard wood, 

 for instance the holly-wood used for scroll-sawing, and note 

 any change of form which occurs. What effect is produced by 

 moistening, in the same way, the other side of the wood ? 



Fill a strong stone bottle with large dry seeds of known weight, 

 for instance beans, and put it in a pail of water so that the 

 water can pass into its mouth. If the bottle should break in a 

 few hours, remove quickly with blotting-paper all the outside 

 moisture from the seeds, and determine their increase in weight 

 due to absorption of water. 



Place a thermometer bulb in a tumbler half full of dry starch ; 

 slowly add to this water of exactly the same temperature, and 

 note any change of temperature which accompanies the absorp- 

 tion of the water by the starch. 



Weigh a fleshy root, and carefull}* dry it in a water- bath, to 

 determine the amount of water which can be expelled at 100 C. 

 Then raise the temperature of the root to somewhat above 

 100 C., by carefully heating it in a sand-bath, and observe any 

 loss of weight. Determine also the amount of water contained 

 in a fibrous root of Indian corn, a small woody stem, " dry " 

 wood, leaves of Indian corn, Begonia, and Sedum, the pulp of 

 an apple, grains of wheat. 



After the above substances have been thoroughly dried and 

 weighed, immerse them in water for one hour, wipe them as dry 

 as possible by means of blotting-paper, and weigh again. How 

 much water can each absorb in one hour? In like manner as- 

 certain how much the}- will absorb in ten hours and in twenty- 

 four hours. 



