360 G. A. Linhart — Rate of the Reduction of 



phosphorous acid. The tubes were then sealed, allowed to cool, 

 the contents well mixed, and the tubes submerged in a thermo- 

 stat kept at 60°. When two consecutive analyses of the mer- 

 curous chloride in the tubes about twenty-four hours apart 

 showed no increase or decrease in the amount of the mercur- 

 ous chloride the reduction was considered complete. More- 

 over, these results always agreed, within 0*1 to 0*05 per cent, 

 with the theoretical amount of mercurous chloride calculated 

 from the mercuric chloride originally present. In a similar 

 manner the concentration of the phosphorous acid* was deter- 

 mined by using an excess of mercuric chloride. 



Reaction Velocity Measurements. — All the experiments 

 were carried out in sealed glass test tabes. As soon as two 

 tubes were filled with 10 cm3 of the standardized mercuric chlo- 

 ride and 10 cm3 of the standardized phosphorous acid, they were 

 sealed, allowed to cool, shaken and submerged in a ther- 

 mostat, where they were held in position by means of coiled 

 brass springs. In the case of the experiments carried out at 

 25° the time t was counted from the moment the tube was 

 submerged until it was removed from the thermostat, while in 

 the experiments at (30° two minutes were allowed for each tube 

 to assume the temperature of the water of the thermostat. At 

 definite intervals a tube was withdrawn, three scratches made 

 with a sharp triangular file in a horizontal plane, on each side 

 of which was placed a folded piece of wet filter paper. The 

 tube was then brought in a vertical position to the point of a 

 small blast lamp flame, care being taken not to allow the upper 

 part of the tube to fly off, as it often contained some mercur- 

 ous chloride. After the tube was thus cracked the upper part 

 was lifted off and the contents filtered and washed (until the 

 wash water was free from chlorine) through an ignited and 

 weighed perforated platinum crucible, fitted with an asbestos 

 mat. After most of the moisture had been exhausted by the 

 aspirator the crucible was suspended in a glass weighing bottle 

 and placed in a drying oven at a temperature of about 80°. 

 The temperature was then gradually raised to 105° and main- 

 tained between 105° and 110° for thirty minutes. 



It is well known that mercurous chloride at that tempera- 

 ture is apt to suffer a slight loss due to volatilization. This 

 loss, however, is almost entirely avoided, first, by drying the 

 mercurous chloride for about 15 minutes by means of the aspi- 

 rator, secondly by raising the temperature gradually in order 

 to avoid the rapid formation of steam, which is apt to carry 

 some of the mercurous chloride with it. Furthermore, the 

 mercurous chloride, being precipitated in this reaction in crys- 



* Of a number of samples of phosphorous acid tested, only one, that fur- 

 nished by J. T. Baker Co., proved sufficiently pure. This consisted of a 

 25 per cent solution, 96 per cent of its total acidity being phosphorous acid. 



