846 Miscellaneous Intelligence. 



ter evolved great heat, sulphurous acid was formed and sulphur 

 evolved. The solid acid in contact with water became diluted, 

 but no sulphurous acid gas was produced. The specific gravity 

 of the acid left in the retort, now sensibly fuming, was 1.8503 at 

 13° R. (G2°F.) ; the acid which distilled over was of specific gra- 

 vity 1.4309, at 11. 5.° R. (58^ F.) 



This fuming acid was formed only in the first half of the third 

 day, fire having been kept in the furnace from seven o'clock in the 

 morning till nine o'clock in the evening, during the two first days, 

 and its formation could not be perceived for a longer period than 

 half an hour. The distillation had been carried on therefore very 

 slowly, and without great care the formation of the anhydrous 

 acid might easily be overlooked. Its formation is thus explained : 

 that by a certain process of concentration of the hydrated sulphu- 

 ric acid, obtained by the previous long and slow distillation, part 

 of the acid takes water from another part, and is volatilized, leav- 

 ing a portion so concentrated as at some particular point to re- 

 solve itself into two parts, one the anhydrous acid, the other 

 acid of the usual degree, or nearly so, of concentration ; the supe- 

 rior volatility of the anhydrous acid, allows it to separate and distil 

 over at the particular time of decomposition: and thus these 

 changes seem effected. — Brewstefs Journal. 



17. Hygrometrical Indications by Sulphuric Acid. — M. A. de la 

 Rive has applied the heat produced by the union of sulphuric acid 

 and water, as a measure of the quantity of water in the atmo- 

 sphere, and in his manner of applying it, has thus constructed a 

 new kind of hygrometer. A very delicate thermometer, with a 

 small bulb, being dipped in sulphuric acid, slightly shaken, and 

 then exposed to the air, will exhibit an elevation of temperature 

 up to a certain point, after which the mercury will fall. M. de la 

 Rive states that the elevation of temperature is proportional to 

 the quantity of water in the atmosphere. Thus supposing the 

 instrument at 12° (53°. 5 F.) when plunged into the acid, and that 

 'by exposure to the air it rose to 25° (78° F.) L e., 13|o (24.5 F.), 

 and that put into a jar containing air of extreme humidity, it rose to 

 27° i. e., a change of 15° (27°F.) the ratio of 13^° to 15°, Avill ex- 

 press that of the tension of the aqueous vapour existing in the air, 

 to the tension of the aqueous vapour in an atmosphere saturated 

 with water. 



For the application of this principle it is requisite that the num- 

 ber of degrees that the thermometer will rise in air saturated 

 with water, at all temperatures, should be ascertained. It is 

 proposed that these should be set down on a thermometer opposite 

 to the temperature of the air in which they were obtained ; then 

 on making an experiment, the number of degrees which the ther- 

 mometer rises in air at any temperature is to be divided by the 



