260 RESPIRATION, FERMENTATION AND DIGESTION 



Take the receiver away, warm the seeds by immersion in 

 water at 35 to 38 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 Quotient. 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. , 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 



