SANGER-RIEGEL. — PYROSULPH. CHLORIDE-CHLORSULPH. ACID. 701 



Two portions of Sample A, the second having remained sealed until 

 used, gave respectively— 38° to— 37° and — 37.5°to —37°, by thecapillary 

 method. Of Sample B a portion melted from —37° to —34.5° by the 

 immersion method. Further precautions in using this method were 

 taken in the examination of Sample C. The tube containing the sub- 

 stance was provided with a two-holed rubber stopper, through one hole 

 of which passed the thermometer. The other hole carried a T-tube, 

 through the vertical portion of which moved the stirrer. Into the side 

 arm was passed a gentle current of dry air, to prevent access of mois- 

 ture to the substance. The melting tube was immersed in a bath of 

 alcohol at a temperature two to four degrees higher than that of the 

 substance. Four determinations with Sample C gave an average of 

 -37.3°. 



The melting point of pyrosulphuryl chloride may be placed, there- 

 fore, at -37.5° to -37°. 



Vapor Density. — The determinations of vapor density were made 

 by the Victor Meyer method at the temperature of boiling aniline 

 (184°). The weighing bulbs and the apparatus were very carefully 

 dried and the eudiometer calibrated. Readings of the volume of air re- 

 placed were not made until the meniscus had long remained constant. 

 The following results were obtained : 



Substance. £-^1^^^ T°. 



1. Sample A 0.0480 g. 5.72 21 



2. Sample A 0.2102 g. 27.53 23 



3. Sample A 0.0625 g. 6.90 23.3 



4. Sample C 0.1382 g. 16.95 26.5 



5. Sample C 0.2501 g. 28.90 27.5 



Calculated for S2O5CI2 



These determinations show that pyrosulphuryl chloride does not dis- 

 sociate appreciably at a temperature of 184°, and it is less likely to do 

 so at its boiling point. The presence of traces of moisture, which are 

 not easy to guard against, would lower the vapor density slightly. In 

 this connection, the addition of phosphorus pentoxide to the bulb of 

 the Meyer apparatus by Prandtl and Borinski *3 is not admissible in 

 the presence of a possible impurity of chlorsulphonic acid, which 

 would thereby be dehydrated. 



Analysis. — A volumetric analysis was made of Sample 3. 1.1657 

 g. substance were prepared for titration as in the analysis of oleum, 

 p. 690. 



