350 On. Crystallography, ( 



gravities. Tf we should desire, however, a greater precision, 

 we might attain it by the method which we shall indicate, 

 in order to assimilate the weight made with any liquid at 

 any given temperature, to the result which would have 

 been given by distilled water at 14° of" Reaumur. 



Having taken precisely the absolute weight of the areo- 

 meter, which will be,, for example, 152 grammes, and 

 knowing the additional weight supposed to be 20 grammesi 

 necessary for levelling it in distilled water at 14°, we shall 

 have for the sum of these two weights 1/2 grammes. 



Let us now suppose that the additional weight which 

 produces the levelling with another liquid is 20*5 grs. the 

 sum will become 172*5 grs. 



Now we know that when a body floats in part, the 

 weight of the volume of the liquid which answers to the 

 part imniersed is equal to the total weight of the body. 

 Thus, since the part immersed is the same in both cases, it 

 results that the weights of the two liquids when of equal 

 volume, or what comes to the same thing their specific 

 gravities, are in the ratio of 1720 to 1725. 



This !)eing done, it is evident at first sight that the liquid 

 substituted for distilled water immediately gives the ahso- 

 'lule weight of the body under examination, without any 

 correction being required. Let this weight be eleven 

 Crammes. After havmg found by a second operation the 

 quantity which the body, weighed in the liquid which you 

 employ, loses of its weight, and which we shall suppose to 

 be 4*7 grs., make this proportion, 1723 : 1720 : : 4*7 : a 

 fourth term which will indicate the loss corrected, or that 

 which the body would have undergone of its weight in 

 distilled water at 14° of Reaumur. This loss, which will 

 be found to be 4*69, will give at the same time the weight 

 of the volume of distilled water at 14", equal to that of the 

 body ; after which you will make this other proportion 

 which returns to that above indicated 4*69 : 11 : : the unity 

 is a fourth term, which will be 2-3434, and which will in- 

 dicate ihe true specilic gravity of the body. By employing 

 no correction, we should have found 2*.3404. 



There are substances which being immersed in water 

 drink up this liquid. Of this nuuibcr is the mesotype 

 (zeolite ofCronstedt). We perceive this property when, 

 having placed the substance in the lower basin E, we sec 

 the areometer descend, after having mounted up, although 

 the cistern A remains loaded with the same weight. Ixx 

 this case we shall allow the body to imbibe the whole 

 quantity of water wliich it can admit into its pores, and we 

 •hall know that it has "cached this kind of point of satura- 

 tion 



