Chemistry and Physics. 253 



two substances are mixed in proper proportions at a low temper- 

 ature, the product is a mobile colorless liquid corresponding to 

 the chlorsulphonic acid of Williamson, and which the', authors 

 call fluosulphonic acid. To prepare it a known quantity of sul- 

 phur trioxide was distilled into a platinum receiver, this was im- 

 mersed in a freezing mixture, and connected with a platinum 

 retort containing hydrogen-potassium fluoride in excess. On 

 heating this, hydrogen fluoride passed into the receiver and com- 

 bined with the trioxide. To free the fluosulphonic acid thus 

 formed from the excess of hydrogen fluoride, it was heated to 

 about 30° and a current of dry carbon dioxide was passed 

 through it. The final ratio obtained was 1 of S0 3 to 1-13 of HF. 

 The analysis of the acid was difficult on account of the extreme 

 violence of its action upon water. Its boiling point was deter- 

 mined to be 162 - 6°; though like chlorsulphonic acid it slightly 

 decomposes at this temperature, forming probably sulphury 1 

 difiuoride. Fluosulphonic acid is a thin colorless liquid, fuming 

 in the air and having a faint pungent smell. It feels greasy to 

 the touch and has but little action on the dry skin ; being entirely 

 without the intense blistering action of hydrogen fluoride. It 

 slowly attacks glass, more rapidly in presence of moisture. It 

 readily acts on lead forming sulphate and fluoride. — J. Ghem. 

 Soc, xli, 921, December, 1892. G. f. b. 



4. On Carbon di-iodide. — It has been observed by Moissan 

 that when carbon tetra-iodide is exposed to the sun's rays in a 

 vacuum, or even to diffused daylight or a temperature of 120° it 

 splits up into carbon di-iodine and iodine. The di-iodide is best 

 prepared, however, by dissolving the tetra-iodide in carbon tetra- 

 chloride and adding the quantity of powdered silver required to 

 abstract half the iodide. It crystallizes in pale yellow nodules, 

 fuses at 185°, volatilizes a little above this and begins to decom- 

 pose at 200°. Its density is 4-38. It is soluble in carbon tetra- 

 chloride, carbon disulphide, ether and hot alcohol. It is not 

 reduced by hydrogen at 200° and is not attacked by chlorine or 

 bromine in the cold. Heated in oxygen it melts and then decom- 

 poses, the carbon burning to C0 2 . Sulphuric acid decomposes it 

 at 200°.— C. R., cxv, 152 ; J. Chem. Soc, xlii, 1291, Nov. 1892. 



G. F. B. 



5. Photographic study of the movement of projectiles. — At a 

 meeting of the Physical Society of Berlin, Nov. 18, 1892, F. 

 Neesen described a new method of studying the movements of 

 projectiles which had been carried out under the auspices of the 

 Prussian Artillery Commission. Inside the projectile near the 

 head which could be unscrewed was placed a sensitive plate. 

 This plate was opposite an opening 0'5 mm in diameter. In a 

 second arrangement a sensitive plate was also placed at the mid- 

 dle of the shot inside it and opposite a small opening which per- 

 mitted the entrance of the sun's rays. The shot was so directed 

 that the sun's rays formed a small image of the sun on the pho- 

 tographic plate. At each turning of the shot in its path, an 



