32 



OSMOTIC PRESSURE OF AQUEOUS SOLUTIONS. 



and short threads. If we multiply the weight of the short thread by 

 the number of times its length is contained in that of the long thread, 

 i. e., by the number of times it was set end to end, and subtract the 



i * 



Fig. 18. — Simplest form of manometer. 

 (1) and (2) bulbs with traps in the bottom to prevent liquids from working their way into the 

 calibrated portion of the instrument; (3) nitrogen reservoir to prevent loss of gas under 

 diminished pressure; (4) mercury filling the portion of tube whose caliber may have been 

 altered in closing the instrument. 



Fig. 19. — Manometer for high pressure. 



Differs from that in Fig. 18 only in having a nitrogen reservoir within the calibrated portion of 



the instrument. 



product from the weight of the long thread, the difference is the weight 

 of the mercury which would be required to fill all the meniscus spaces 

 which were left vacant in setting the short thread end to end along 

 the tube. Converting this difference in weight into volume, and divid- 



