46 Mr. Griffin's Apparahis for the Formatim of Water. 



with oxygen gas the principle gas-holders and receivers which may 

 happen to bo in common use. The quantity of mixture in grains 

 required for each vessel is found by multiplying the capacity of the 

 vessel, expressed in cubic inches, by 1*75. Thus, if 100 cubic inches 

 of gas are required, the quantity of black mixture to be taken is 

 100 X 1*75 (or 100 + 50 + 25) = 175 grains. For a cubic foot of 

 gas, the quantity of mixture required is 1728 X 1*75 (or 1728 + 864 

 + 432) = 3024 grains. In other terms, if x is the capacity of a gas- 

 holder, expressed in cubic inches, then the arithmetical equivalents of 

 X -{- Ix -\- Ix show the number of grains of the black mixture neces- 

 sary to be taken to fill the gas-holder with oxygen. 



When a large quantity of gas is required, it is best to divide the 

 mixture into several tubes, so as not to heat more than 500 grains 

 of it at once ; otherwise the disengagement of gas is inconveniently 

 rapid. 



XIV. — Description of an Apparatus for Exhibiting the Formation of 

 Water by the Combustion of Hydrogen Gas in Atmospheric Air. 

 By John Joseph Griffin. 



Convenient methods of demonstrating well-known facts are often of 

 importance to teachers of chemistry. This principle has induced me 

 to present the following little apparatus, which may sometimes bo found 

 useful on the lecture-table. The figure represents a combination of 



glass tubes, of which the tube, o, e, g, is about 10 inches long and 

 I inch wide, and the tube, c, o, about half-an-inch in the bore. 



A current of hydrogen gas, dried by chloride of calcium in the 

 tube, a, issues from the blow-pipe jet, i, and is inflamed. The flame 

 should be about \ inch long. The tube, c, must bo fixed vertically 

 over the flame. The tube, o, Cy g, must be quite dry. The tube, f, 

 must contain cold water. The diameter of this tube is a little less 

 than that of tlie tube in which it is placed. It is fixed in its position 

 by two small cork wedges, at/ g, which are cemented to the tube,/ 



The heat of the flame causes the atmospheric air to rush into the 

 vertical tube, c. The oxygen of the air combines with the burning 

 hydrogen, and forms water, which passes, in the state of steam, mixed 



