go COHESION OF FLUIDS. 



Application of would perhaps be equivalent to the pressure of aboiit one--» 



the dootrme i,^i,^(ii.e(]fl-i of 3^ inch, and nai^ht reduce the height from 2 to 



to particular ' '^ ° 



fluids. • about I9, and the weight in the same proportion. There is, 



however, as gr^at a diversity in the results of different expe- 

 riments on the force required to elevate a solid from the sur- 

 face of a fluid, as in those of the experiments ill capillary 

 tubes : and, indeed, the the sources of error appear to be 

 here more numerous. INIr. Achard found that a disc of glass, 

 one inch and a half French in diameter, required, at 69° oi 

 Fahrenheit, a weight of 91 French grains to I'aise it from the 

 surface of the water; this is only 37 English grains for each 

 square inch ; at 44i° the force wa« -,^-^ greater, or 39 gtarns 

 End a half; the difference being ^-^j for each degree of Fah- 

 renheit. It might be inferred from these experiments, that 

 the height of ascent in a tube of a given bore, which varies 

 in the duplicate ratio of the height of adhesion, is diminished 

 about t|-5 for every degree of Fahrenheit that the temperature 

 is raised above 50°; there was, however, probably some con- 

 siderable source of error in Achard's experiments, for I find 

 that this diminution docs not exceed Totro- The experiments 

 of Mr. Dutor make the quantity of water raised equal to 44.1 

 •grains for each square inch. Mr. Achard found the force of 

 ndhesion of fulfuric acid to glass, at 69° of Fahrenheit, 1.2^^ 

 that of water being 1, hence the height was as 69 to 1, and 

 its square as .47 to 1, which is the corresponding proportion 

 for the ascent of the acid in a capillary tube, and which docs 

 not very materially differ from tlie proportion of 395 to 1, 

 assigned by Barruel for this ascent, Musschenbi\)ck found it 

 .8 to 1, but his acid was probably weak. For alcohol the ad- 

 'honoti was as .593, the height as .715, and its square as 

 '.510 ; the observed proportion in a tube, according to an ex- 

 ■perirnent of Musschenbroek, was about .550, according to 

 t.'arre from .400 to .440. The experiments on sulfuric ether 

 \lo hot agree quite so well, but its quality is liable to very 

 considerable variatrons. Dutour foUnd the adhesion of alco- 

 hol .58, that of water being 1. 



With respect to mercury, it has been shown by Professor 

 Casbois of Wetz, and by others, that its depression in tubes of 

 glass depends on the imperfection of the contact, and that 

 when it has been boiled in the tiibc often enough to expel all 



foreign 



