148 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



removed by a stream of water flowing through properly- 

 arranged pipes; and while the air is expanding and cooling 

 in the other space, heat is abstracted from whatever has been 

 placed in a second properly arranged receptacle. The only 

 limit to the temperature attainable is the conducting power 

 of the material of which the ajDparatus is composed. The air 

 contained in the j^istons may be at any pressure that the ap- 

 paratus can withstand. The machines built for cooling large 

 masses of water for the use of breweries, etc., are usually 

 worked at from 100 to 120 pounds per square inch, the efiicien- 

 cy and capacity of the machine increasing with increased 

 pressure. To keep up this pressure and meet leakage, a small 

 compressing pump draws air through two' boxes containing 

 chloride of calcium. This is necessary to dry the air, for if the 

 air be damp the moisture is deposited as snow in certain 

 parts of the apparatus, and causes mischievous obstructions. 



A NEW ICE CALOKIMETER. 



The ice calorimeter in all its forms measures quantities 

 of heat by determining how much ice that heat can melt. In 

 Bunsen's apparatus advantage is taken of the change of vol- 

 ume which ice undergoes upon fusion. This change occurs 

 at one end of a column of mercury sustained in a capillary 

 tube : as the ice melts the mercury descends, and the amount 

 of fall represents the quantity of heat. But the use of a cap- 

 illary tube in this apparatus affects the delicacy of all meas- 

 urements made with it. So Schiiller and V. Wartha propose 

 a modification of Bunsen's calorimeter, in which graduated 

 scales are done away with, the amount of mercury involved 

 in any measurement made with the instrument being de- 

 termined by direct weight. As the ice in the apparatus 

 melts and the column of mercury falls additional mercury 

 flows in through a peculiar suction tube, and the weight thus 

 absorbed affords a measure of the heat. The details of the 

 new calorimeter are not very complicated, but need the au- 

 thor's diagram for their explanation. The inventors tried to 

 apply their instrument to determining the specific heat of 

 some metallic titanium, and obtained a value apparently too 

 high. Seeking the cause of their error, they found that the 

 supposed metal contained nitrogen, being really a compound 

 of the formula TiNg. 35 (7, September, 1875. 



