INFLUENCE OF CARBON DIOXIDE 



43 





K 



chamber is one-fifth oxygen at the beginning of the test, while 

 the drop of water in which the material is mounted as well as the 

 cell sap is saturated with the 

 free element. The result of 

 the exclusion of the oxygen of 

 the air from the cell is not ap- 

 parent therefore, until this has 

 been used, and may need sev- 

 eral minutes. Carbon dioxide 

 however, has a slightly poison- 

 ous action, and it may be seen 

 that movement is inhibited 

 more quickly in this gas than 

 in hydrogen. 



59. Influence of Carbon Di- 

 oxide upon Protoplasm. In 

 order to secure absolutely pure 

 carbon dioxide the following 

 method should be used. Put 

 about 300 g. potassium bicar- 

 bonate in a small retort. Con- 

 nect the retort with a small v 



FIG. 23. Kipp s apparatus for produc- 



gasometer by a tube which tion of carbon dioxide, or hydrogen. Mar- 

 ble or zinc is placed in the upper chamber, 

 K, and a solution of hydrochloric or sulphuric 

 acid in the lower chambers. Air is forced 

 in through the tube with the stop-cock H^ 

 until the acid rises and covers the marble or 

 metal, when the stopcock is closed. The 

 gas passes directly out through the upper 



atmospheric gases with which tube with the stopcock H Open the stop . 



cock H l when sufficient gas has been pro- 

 duced, and the acid will return to the lower 

 chambers. The manometer connected with 

 the lower chamber is useful in testing the 

 connections and shows the pressure at any 

 time. 



has been bent into two acute 

 angles, and the connections 

 made secure. Fill the gas- 

 ometer with water that has 

 been boiled to drive off the 



it is saturated. The inlet tube 

 of the gasometer should be 

 furnished with a three-way 

 cock. Heat the retort with a 



small gas stove or bunsen 



burner. Open the three-way cock and allow the gas to pass out 



