Djxon and Ball — Heat produced during Inversion of Sucrose. 157 



capsules, which were found to be quite satisfactory, were constructed in the 

 following manner : — 



About 1 cm. from the lower ends of the glass tubes containing the wires 

 of the thermocouple little copper bands were cemented to the glass with 

 Canada balsam, in order to support the lower ends of the capsules. The 

 upper and lower ends of the capsules were formed of discs of cork 2 cm. in 

 diameter. The lower ones were perforated by holes, into which the glass 

 tubes fitted tightly. The upper ones had holes sufficiently large to allow the 

 copper bands to pass through, and to these discs silk threads were 

 attached, for the purpose of rupturing the capsules. Cylinders, 6 cm. long, 

 which fitted tightly on the cork discs, were made of a double thickness 

 of paper, with the edges cemented with seccotine. The upper ends of the 

 paper cylinders were notched and turned over on the upper corks, leaving 

 the lower ends open. The cylinders were then immeised in melted paiaffin- 

 wax, and the beaker which contained it was placed under the receiver of an 

 air-pump, which was then exhausted. This removes all air-bubbles from 

 the paper, and ensures that it is thoroughly impregnated with wax. The 

 capsules were then removed, and allowed to cool. In order to assemble the 

 capsules on the tubes of the thermocouple, the tubes were passed through 

 the holes in the upper corks, which were now firmly attached to the paraffined 

 paper. The lower corks were then pushed on to the tubes until they came 

 into contact with the copper bauds, and the edges of the discs were 

 smeared with vaseline. The open ends of the capsules were then pushed 

 over the lower cork discs until the ends of the paper capsules projected 

 about 0"5 cm. The whole thermocouple was then inverted, and the cup- 

 shaped space left below the lower cork was filled with melted paraffin-wax 

 of a low melting point. This effectually seals the lower ends of the capsules. 

 For the purpose of filling the capsules, there is sufficient space between the 

 glass tube and the edge of the hole in the upper cork to insert the end of a 

 small pipette. The capsules used held 15 c.c. of liquid, and, after filling, the 

 hole at the top round the glass tube was sealed with paraffin-wax. 



If carefully made, these capsules give no trouble due to leakage, and are 

 easily opened by pulling the silk thread. This separates the paper cylinder 

 from the lower cork, which is held by the copper band, and allows the enzyme 

 solution to mingle rapidly with the surrounding liquid. 



Flasks. 



- The flasks used were the ordinary so-called pint-size vacuum flasks, which 

 are made of silvered glass, enclosed in a metal case. The conductivity 

 constants of the two flasks were found to differ by about 9 per cent. Unless 



