260 RESPIRATION, FERMENTATION AND DIGESTION 



Take the receiver away, warm the seeds by immersion in 

 water at 35 to 3 8° C. for five minutes, then replace and set large 

 flasks or dishes full of hot sand inside the receiver. Make con- 

 nections and estimate the proportion of oxygen and carbon dioxide 

 present at the beginning and three hours later. Make tempera- 

 ture records. Compare results at the three temperatures. 



329. Estimation of the Respiratory ttuotient. The following 

 method designed by Puriewitsch will be found most convenient 



Fig. ,128. Apparatus -for the determination of respiratory quotient under the in- 

 fluence of various nutrient solutions. A, receiver, an Erlenmeyer flask, into which 

 projects three glass tubes. The shortest tube merely passes through the stopper and 

 is closed externally by a section of rubber tubing and a pinchcock. A longer tube 

 extending just above the surface of the fluid in the flask is connected at D with a 

 manometer C. B, burette, with a three-way stopcock at a. The lower end of the 

 burette is connected by a strong rubber tube with a short thistle tube, E. The free 

 arm of the stopcock a is bent and the end curved upward, the tip being immersed in 

 a small dish of mercury at b. After Puriewitsch. 



for estimation of the respiratory quotient. Secure an Erlen- 

 meyer flask of a capacity of about 200 cc. and provide it with a 



