546 Intelligence and Miscellaneous Articles. 



acid, the gas, well- washed, should be passed through Woulf s bottles, 

 containing distilled water and cuttings of zinc. In this operation the 

 following appearances occur : the metal at first tarnishes and is co- 

 vered with a grayish crust ; the liquor then becomes slightly yellow, 

 but not turbid ; the colour increases until it becomes as deep as that 

 of a concentrated solution of chromate of potash, and it continues as 

 long as there is great excess of sulphurous acid in the liquid. If the 

 disengagement of gas slackens, or if by the increase of temperature 

 the metal is more rapidly dissolved, the colour diminishes, and in 

 the first case the liquid becomes turbid and a white pulverulent de- 

 posit is formed ; if the operation be now stopped, or if the liquor be 

 suffered to remain at rest during a night, this white powder is con- 

 verted into white brilliant prismatic crystals, which collect on the 

 sides of the vessel and on the undissolved portions of the metal. 



Examination of these Crystals. — They are easily obtained in con- 

 siderable quantity, either by spontaneous evaporation or cautious 

 evaporation in a water-bath ; much sulphurous acid is evolved, and 

 the surface of the solution is covered with a thick layer of crystals. 

 These crystals may be washed with water, for they are almost in- 

 soluble in it ; but water containing sulphurous acid dissolves them 

 readily, without becoming coloured ; these crystals are colourless, 

 inodorous, transparent and insoluble in alcohol ; acids decompose 

 them with the evolution of sulphurous acid, without any deposit of 

 sulphur ; the solution in hydrochloric acid gives no precipitate with 

 chloride of barium. When the crystals are moist they are readily 

 converted into sulphate by exposure to the air, but when dry they 

 may be long kept without alteration. 



The preceding facts prove that these crystals consist of sulphurous 

 acid, oxide of zinc and water ; to analyse them the oxide of zinc was 

 obtained by calcination, the sulphurous acid by converting into sul- 

 phuric by means of iodine, and noting the quantity absorbed, and 

 the water by calculation ; this it would be almost impossible to ob- 

 tain directly, for the sulphurous acid is disengaged at about the same 

 temperature. 



The salt appeared to be composed of 



One equivalent of sulphurous acid .... 32 



One equivalent of oxide of zinc 40 



Two equivalents of water 18 



Equivalent .... 90 



Examination of the Mother-water. — The solution from which the 

 sulphite of zinc has been separated is colourless, transparent and in- 

 odorous, contains no sulphuric acid ; and the examination proved 

 that when sulphurous acid acts upon zinc two salts only are formed, 

 the sulphite and hyposulphite ; when, however, the mother- water is 

 further evaporated, it yields different products according to the tem- 

 perature at which it is effected, yielding sulphurous acid, sulphite of 

 zinc and other products. — Journ. de Ph. et de Ch., Octobre 1843. 



