169 



Improved Forms of Maximows' Automatic Pipette. 



F. M. Andrews — Indiana University. 



Grafe' figures and describes the automatic pipette of Maximows 

 (Fig. 1). The pipette as given by Maximows is very practical but is 

 in part difficult of manipulation and needs some improvements, which 

 I have supplied. In the first place a Woulfe bottle with three openings 

 at the top is not necessary nor is a bottle with a tubulure at the base 

 absolutely essential, although it is convenient. Any bottle having an 

 opening at the top and provided with a stopper having four holes is 

 sufficient. The funnel shown in Maximows' drawing is also unnecessary. 

 If, as Grafe describes, one closes A and B (Fig. 1), and opens C the 

 NaOH in D flows out, creating a partial vacuum in D and causing the 

 desired solution, in this case baryta water, to rise in the pipette E if 

 the pinch cock F is open. If now one opens B air will enter D, allowing 

 the solution in E to sink and thus measure the quantity of fluid. In 

 this last operation is the chief difiiculty, for when B is closed after 

 opening the solution in E will generally not cease to sink at once owing 

 to the reduced pressure in D produced by the column of solution in E. 

 Since accuracy is the prime consideration here a slight error is fatal for 

 correct results. Furthermore the glass tube B should extend below 

 the surface of the NaOH or KOH solution to insure the removal of all 

 COi and the outside air not be allowed to enter too rapidly. Also it 

 will be seen according to Fig. 1 that the NaOH or KOH solution would 

 be wasted in the Maximows apparatus. The control of the outflow of 

 the solution in E should be for the sake of accuracy and convenience 

 not at B but at the lower end of the pipette E. Maximows used the 

 funnel A for refilling, which is unnecessary. 



The above difficulties I have removed by a modification of Maximows' 

 apparatus as shown in Figs. 2, 3, and 4, which I will now briefly de- 

 scribe. In both Figs. 2 and 3, which are photographs, bottles with 

 one opening at the top could be used instead of the Woulfe bottles. 



^ Grafe, Dr. Viktor — ErnahrunKsphysiolosisches Praktikum der hoherer Pflanzen, 

 p. 360. 



