SANGER-RIEGEL. — PYEOSULPH. CHLORIDE-CHLORSULPH. ACID. 709 



liquid air tube there was still much hydrochloric acid, some chlorine, 

 and a few particles melting at —13°. Two subsequent distillations at 

 low pressure resulted in a product reacting quietly and completely 

 with water, leaving no oil. There was not much decomposition, but 

 evidence of a little sulphuryl chloride. The crystallizing point was 

 —80°, the melting point —70°. This product, distilled in the dry sys- 

 tem (Figure 2) boiled at 65° to 69° (14-17 mm.), and, at 76S mm., the 

 first half came over at 137-151° ; the second at 151-152°, There was 

 very little residue and very little in the U-tube, chiefly hydrochloric 

 acid. On cooling, no vitreous body separated, but only the crystalline, 

 and at —75°. That there was probably sulphuryl chloride present 

 was shown by a redistillation, from which a portion was obtained boiling 

 from 103° to 141° and melting at —52°. Analysis of the product showed 

 too low chlorine and too high sulphur, as in Preparation 12, and the 

 two preparations were probably similar. 



A study of the remainder of Preparation 13, by repeated distillations 

 at very low pressure, showed an increasing tendency to decomposition, 

 and, indeed, more in the direction of equation (1) (page 703). The 

 boiling point was 60° to 64° at 2 to 4 mm. The details need not be 

 considered here, but there was clear evidence of more hydrochloric acid 

 and sulphur trioxide, with less sulphuryl chloride. The amount of 

 chlorine, by analysis, in the main body became less ; the sulphur higher. 



The deleterious effect of distillation at low pressure was strikingly 

 shown in the treatment of Preparation 14. This crystallized readily with- 

 out giving the vitreous solid, and melted at —80°, corr. After distilla- 

 tion at 68-70° (15-17 mm.), the product would not crystallize at all, 

 even on inoculation with crystals from another preparation. The spe- 

 cific gravity was 1.782 at 20°, showing the probable presence of sulphur 

 trioxide. 



Fractional Crystallization of Chlorsulphonic Acid. — It seems there- 

 fore certain that chlorsulphonic acid cannot be purified by distillation, 

 that it is an unstable body, and that even the purest specimens here- 

 tofore obtained, including our own, must have been contaminated by 

 the dissociation products. 



The boiling point must be always somewhat in doubt. In order to 

 obtain identifying constants which would be less affected by temperature 

 and pressure, e. g., the melting point and specific gravity, we had re- 

 course to fractional crystallization. 



200 g. of Preparation 17 became viscous at —132°, crystallized at 

 —100°, and melted at —72°. The entire amount was brought to crystal- 

 lization and then partly melted. 83 g. of solid were then drawn out of 

 the melted mass by a spirally bent glass rod previously inserted. These 



