Art. XLII. — Cahrimetric Iiwestigatioyis ; by R BuNSEN.* 



The Ice Calorimeter. 



Ix order first to become better acquainted with the|'lu'ii<>!in'ii;i 

 attending the formation of ice, although only in so Ihr as tlu'v 

 couie under consideration in using the instrument, the calori- 

 meter, containing a cylinder of ice and carefully surrounded 

 with snow, was kept long under observation. It stood, as in all 

 the following experiments, in a large earthenware decanting 

 jar, through whose lower orifice the water droj^ping from the 

 melted snow could coiitinuall;y- flow off, so tliat a contact l)e- 

 tween the lower part of the instrument and tlic water thu.s 

 formed was not to be feared. The instrunu'iit soon sMrnHinds 

 itself with a coherent mass of semisolid snow (tinicisi. II. 

 after twelve or fifteen hours, a considerable cavitv has !>. . : 

 formed on the walls of the jar bv the external meltinc- ,,r t 

 mass, this cavity is then increased by sniootliin,!: otV the lo,,.. 

 coherent substance with a spatula-shaped stick, the porn -: - 

 thus scraped off being stuffed into the vaeent spaces under r* ■ 

 calorimeter, and the snow lost by meltin.u' replaced with iVesh. 

 The fii-st experiments were made with freshlv thllen snow, which 

 liad been collected from a clean substratum of the same sub- 

 stance, and (jarefully shielded from every contammation aris- 

 ing from the soil. Of this snow, one hundred weight was pre- 

 served in a clean wooden chest, as a stock for the refilhngs 

 diinng the experiments. With such a stock the calormieter 

 niay by filfing up twice daily, be kept for weeks m continual 

 use without the necessity of renewing the ice-cylmder. 



Throughout the entire duration of the observations, which 

 occupied five days, the inner vessel enclosed in the lee-eyhnder 

 was kept closed "with a rubber stopper, and the wliole m>tru- 

 J^ent, with the exception of the scale, surrounded on all .-kIcs 

 with melting snow. The temperature of the room in which the 

 obser;^ations were made varied between 0°-5 C. and 6 • C. 1 he 

 observations are presented in the following table 1. Column i, 

 contains the time of the observations in hours. Column il 

 gives the readings of the calorimeter scale for these times ; the 

 observed values are characterized by a star, the others have 

 oeen calculated from these by interpolation. Up to the tliirt\ - 

 fi^t hour the mercury which lelt the graduated tube was 

 je'gbed; and the weight thus found transformed uito scale- 

 d^Tisions according to equation (1). Column IH has been cab 

 ^^lated with the aid of equation (3), and gives the weight of 



