348 Dr. Ure on the Ultimate Analysis of [May, 



of the ignition from one end to the other being proportioned to 

 the expansion of glass, so that the tube very seldom cracks in 

 the process. Indeed I have often used the same tube for a 

 dozen experiments, in the course of which it became converted 

 into vitrite, or Reaumur's porcelain." 



Since the evolved gas is saturated with moisture, Dr. Ure 

 reduces it to the volume of dry gas, by help of a table, which he 

 gives, computed by the well-known formula from his table of the 

 elastic force of steam, published in the Phil. Trans, for 1818. 



In certain cases, where the quantity of hydrogen is small, or 

 where, as in the example of indigo, its presence has been denied, 

 Dr. Ure employs pulverulent calomel instead of peroxide of cop- 

 per. " The organic compound being intimately mixed with that 

 powder, and gently heated, the muriatic acid gas obtained de- 

 monstrates the presence, though half of its volume will not give 

 the total quantity of hydrogen ; for a proportion of this elementary 

 body continues associated with oxygen in the state of water." 



Dr. Ure next gives, in detail, one example of the mode of 

 computing the relation of the constituents from the experimental 

 results, and then states the other analyses in a tabular form. 



" 1-4 grain of sulphuric ether, specific gravity 0'70, being slowly 

 passed in vapour from the ^glass bulb through 200 grains of 

 ignited peroxide of copper, yielded 6-8 cubic inches of carbonic 

 acid gas at 66° Fahr. which are equivalent to 6-57128 of dry gas 

 at 60°. This number being multiplied by 0' 127 = the carbon 

 in one cubic inch of the gas, the product 0-8345256, is the 

 carbon in 1-4 grain of ether; and 0-8345256 x 4 = 2-2254 

 = the oxygen equivalent to the carbonic acid. The tube 

 was found to have lost 4*78 grains in weight, 0-1 of which 

 was due to the hygrometric moisture in the oxide, and 1-4 to the 

 ether. The remainder, 3-28, is the quantity of oxygen abstracted 

 from the oxide by the combustible elements of the ether. But 

 of these 3-28 grains, 2-2254 went to the formation of the carbonic 

 acid, leaving 1*0546 of oxygen, equivalent to 0-1318 of hydro- 

 gen. Hence, 1-4 ether, by this experiment, which is taken as 

 the most satisfactory of a great number, seem to consist of 



Carbon 0-8345 



Hydrogen 0-1318 



Water 0-4337 



And in 1 grain we shall have 



Carbon 0-5960 . . . 



Hydrogen. ..0-1330 ..., 

 Oxygen 0-2710 ... 



1-0000 3-75 



