570 



SCIENCE 



[N. S. Vol. XXVII. No. 693 



A Galvanometer Scale for the Direct Bead- 

 ing of Temperatures with Thermo-elec- 

 tric Couples: Anthony Zelent, Univer- 

 sity of Minnesota. 



An accurate scale for use with thermo- 

 electric couples for the direct reading of 

 temperatures is obtained by making the 

 magnitude of the individual scale divisions 

 proportional to the first differential coeffi- 

 cient, de/dt, of the equation for the par- 

 ticular couple employed. 



With the proper resistance in the circuit, 

 and with a galvanometer in which the 

 deflections are proportional to the current, 

 any number of siich consecutive divisions 

 represents the deflection produced when the 

 temperatures of the junctions are those 

 indicated by the lines at the extreme ends 

 of those divisions. 



The movable scale is set, when the circuit 

 is open, to indicate the temperature of 

 the known temperature junction, and then 

 when the circuit is closed, the reading ob- 

 tained indicates the temperature of the 

 other junction. 



The Use of the Bunsen Ice Calorimeter for 



Accurate Heat Measurements: H. T. 



Baenes and Franklin H. Day, McGill 



University. (Read by title.) 



In applying the Bunsen ice calorimeter 

 for some measurements of the heating ef- 

 fects of some of the radioactive changes an 

 effort was made to eliminate the uncer- 

 tainty which always appears in the want 

 of steadiness of the reading. It is a well- 

 known fault with this type of instrument, 

 that the readings are never steady, but 

 have always to be corrected for a slow 

 freezing or melting going on inside the in- 

 strument. The creep or "gang" may be 

 reduced in several ways: Bimsen, 1871, 

 used air-free water and applied a consid- 

 erable hydrostatic pressure, and still ob- 

 tained a constant increase in reading 

 (freezing). 



SchuUer and Wartha, 1888, used the 

 same apparatus with water not air-free and 

 obtained a continuous decrease in reading 

 (melting). Boys, Mond, Ramsay and 

 Shields found a continuous increase in 

 their instrument and compensated for it 

 by surrounding the bulb with an air jacket, 

 thus balancing the freezing by a continuous 

 melting. 



Dieterici used a modified form of the 

 Dewar flask, surrounding the calorimeter 

 with a vacuum jacket and thus consider- 

 ably reduced the creep. 



One of the authors, with Mr. Lucas, had 

 previously made an effort to reduce the 

 creep by surrounding the calorimeter with 

 freezing-point mixtures of great purity, 

 such as clean, freshly fallen snow and dis- 

 tilled water, but had not succeeded. It 

 occurred to the authors, after trying tap 

 water with and without air, and water 

 from the clean blocks of melted river ice, 

 all without success, that it was better to 

 use distilled water, eliminate so uncertain 

 a quantity as the dissolved air, and add a 

 very small quantity of cane sugar to the 

 water before filling the bulb of the instru- 

 ment. 



After several trials with various 

 strengths, we found that a solution of cane 

 sugar containing .18 gram to the liter prac- 

 tically did away with the creep when the 

 instrument was immersed in clear, cracked 

 river ice and tap water. The capillary 

 tube of the instrument had a bore of 

 .0006619 c.c. per millimeter, and the actual 

 change in reading which we obtained was 

 less than 5 mm. in 14 hours, and was con- 

 stant for over two days. Changing the 

 height of the capillary tube was found to 

 have only a very small effect on the creep. 



The authors strongly recommend to those 

 desiring to use the Bunsen ice calorimeter 

 that the bulb be filled with a solution con- 

 taining from .15 to .18 gram per liter, and 

 boiled free from air. The solution is so 



