LAWSOX CHEMICAL RELATIO^^S OF HEAT. 437 



Professor Lawson entered into a full description of sulphur 

 dioxide, which is always produced as a gas when sulphur is burnt 

 in the air or oxygen ; it is also produced in the burning of coals 

 containing pyrites or sulphur compounds ; and the wilting of house 

 plants, and probably the occurrence of coughs and colds in winter, 

 are to some extent due to its occurrence in sitting rooms. Its old 

 name is sulphurous acid gas. It is known also by the names of 

 sulphurous oxide, sulphurous anhydride, <&c., but every one is 

 familiar with it by smell, as that of the *' smell" of burning sulphur. 

 The gas extinguishes flame, and the burning of sulphur is a com- 

 mon remedy for extinguishing a fire in a chimney. However, 

 several metals will burn in the gas, decomposing it — as, for example, 

 potassium, which forms polysulphide, sulphate, and thiosulphate ; 

 when simply heated to about 2200°, it is decomposed into free S 

 and O. It has decided bleaching properties, and is used for wool, 

 silk, sponge, isinglass, and other animal substances that would be 

 injured by chlorine ; also for straw hats and vdliow baskets. A 

 solution of the gas wall remove fruit stains and wine stains from 

 linen. It acts as a disinfectant, an antiseptic, and has been used 

 in preserving meat ; it is also an arrester of fermentation, on 

 account of which wine and beer casks are sulphured, and sulphites 

 are used in breweries and sugar factories. It preserves vellum and 

 catgut. One of its most remarkable effects is that produced by 

 its inhalation ; it is not only irritating, like hydrochloric acid gas, 

 and suffocating, like chlorine, but, when inhaled in a concentrated 

 form, it immediately produces catarrh and sore throat, with all the 

 ordinary symptoms of the natural malady, from which both the 

 Professor and his assistants (Messrs. Lindsay and Stewart, medical 

 students) had suffered more or less during successive investigations. 



The gas is 2 J times the weight of atmospheric air (sp. gr., 

 2*25). It is very soluble in water, which absorbs about 40 times 

 its bulk of the gas at ordinary temperatures ; the solution, when 

 exposed to air in a bottle, changes slowly to solution of H 2 S O 4. 

 At low temperatures a crystallized hydrate of sulphurous acid is 

 obtained. In preparing the gas for condensation, the tubes must 

 be kept dry, otherwise this hydrate forms in them and stops them 

 up. At zero F, which may be readily attained by a freezing 



