296 Miss E. M. Walton on Liquefaction and Cold 



cork supports and having an air-space around and under it. 

 Each of these vessels, containing a glass beaker of smaller 

 diameter (also on cork rests), is furnished with a closely-fit- 

 ting cork cover, perforated to admit a thermometer and a 

 slender wooden stirrer consisting of an upright rod with cross 

 arms at bottom, like a pug-mill. 



The thermometers have each a long stem with the scale on 

 the upper part, so that readings even to —40° C. can be taken 

 without raising the bulb from the mixture. 



The tank is kept filled with water*; and this is frequently 

 agitated by a stirrer moved with a crank. The stirrer re- 

 volves horizontally in the bottom of the tank; and having two 

 blades like a propeller, it agitates the water thoroughly from 

 bottom to top, the moistened part being always immersed. 

 Over the whole is a closely-fitting wooden cover, also perforated 

 for the thermometers and stirrers. 



The salts to be mixed, after finely pulverizing, were placed 

 in separate beakers within the calorimeter, and left for a time 

 to acquire a uniform temperature. The contents of one 

 beaker were then added to those of the other, the cover 

 replaced as quickly as possible, and the whole mixed vigor- 

 ously by twirling the stirrer. Liquefaction generally took 

 place in five to ten minutes; and observations of time and 

 temperature were then taken, slight agitation being still con- 

 tinued. There being four beakers, two experiments can be 

 carried on at the same time; and as the cover is not in a 

 single piece, one portion can be removed without uncovering 

 the other pair of beakers. 



Equivalent weights were taken, seventy grams being used 

 at first; but this was afterward increased to one hundred grams. 



From the following observations it will be seen that the 

 amount of radiation and convection is so small that it may be 

 disregarded.. 



Mixture of Mn(N0 3 ) 2 . 6H 2 with Na 2 C0 3 . 10H 2 O. 

 Temperature of water of calorimeter, 18° C. 



Time. 



Temperature. 



min. 



19 C. 



4 „ 



- 9 



5 „ 



-10 



6 „ 



-10-5 



10 „ 



-10-5 



11 „ 



-10 



21 „ 



- 7 



25 „ 



- 5 



3r of any decided 



temperature may be used, 



