'^ ^M'!'^; W6\mM'lJl?. Dalton's new Method of 



'wafei^tne^e IS' ll( decrease of volume amounting to 6*22 grains 

 by measure; therefore the preceding way of calculating the 

 specific gravity, when the quantity of water and nitrate are 

 known, will be incorrect, as there is no allowance made for the 

 condensation which takes place when the nitrate dissolves. 



The following formula will give the solution to this calcu- 

 lation. Let X = the specific gravity of the solution ; W = 

 the weight of salt; w = the weight of water ; V = the volume 

 of salt; V = the volume of water; and C = the volume of con- 



W + w 

 densation. Then .r = v^ n — ^^^ specific gravity of 



the solution. ' 



Thus if 100 grains nitrate of potai^h, specific gravity 2*074<, 



be dissolved in 500 grains water, required the specific gravity 



of that solution. Now it is known by experiment, that when 



100 grains of the nitrate dissolve in 500 grains water, there is 



a condensation of 622 grains by measure. Therefore 



100 + 500 , ,«^ I -J 



\ - ^ = 48^2r+:5"00^6~^22 = ''^^^^ '^'^ ^'"^"";"^ 



specific gravity; and as this calculated specific gravity differs 



3 

 only T-r-rr parts from that obtained by experiment, I think 



it goes far to prove that there is generally a certain conden- 

 sation or expansion when a salt dissolves, though not in the 

 proportion Dr. Dalton has given. 



In order to find the amount of condensation or expansion 

 when a salt dissolves, the specific gravity is first ascertained 

 as accurately as possible, and after this the increase of volume, 

 when a certain quantity is dissolved in the water contained in 

 the bulb and stem of the apparatus. From these two known 

 quantities, the increase of volume more than that occasioned 

 by the volume of the salt, oi', as I call it, the expansion or 

 the decrease of bulk less than that indicated by the volume or 

 the condensation, may be calculated. Thus if 100 grains of 

 nitrate of potash, specific gravity 2*074', be dissolved in 430 

 grains of water, and give an increase of bulk from the lowest 

 mark of 41*99 grains, the condensation in this case will equal 

 6*22 grains by measure, for 100 grains of the nitrate = 48"21 

 grains of water bulk for bulk; and as there are only 41"99 

 grains indicated by the narrow tube for 100 grains nitrate of 

 potash, there is a condensation of 6*22 grains measure: or 

 100 grains of the nitrate combine with 430 grains of water, 

 the bulk of the whole becoming 471*99 grains measure; and 

 as the whole volume, if there had been no condensation, would 

 have been equal to 478*21 grains measure, according to the 



