42 Historical Sketch of Improvements in [July, 



absorbs oxygen, when afterwards exposed to the air, doubtless 

 occasions the combustion. 



14. Hyposulphites, — Mr. Herschell has pubhshed an excellent 

 set of experiments on these curious salts, and has made us much 

 better acquainted with them than we were before. He has 

 found that if quicklime, sulphur, and water, be boiled together for 

 some time, and if through the filtered liquid a current of sulphu- 

 rous acid gas be passed, the colour of the liquid is destroyed, 

 and it becomes a solution of hyposulphite of lime in water. By 

 evaporation, this hyposulphite is obtained in crystals. It was by 

 means of this salt that most of the hyposulphites which he sub- 

 jected to examination were formed. 



The hyposulphites seem to be mostly soluble in water. Their 

 taste is either mtensely bitter, or intensely sweet. 



(1.) Hifposnlphitc of Lime. — This salt usually crystallizes in 

 irregular six-sided prisms, whose faces are inclined to each other 

 at angles of 141° 39'; 110° 45', and 107° 36'. They refract 

 doubly. They dissolve veiy readily in water; that liquid at 

 the temperature of 37° dissolves nearly its own weight of them, 

 and during the solution, the thermometer sinks to 31°. The 

 specific gravity of a saturated solution at 50" is 1'300 ; and 

 when the specific gravity is 1*114371 at 60° of temperature, the 

 solution contains 0*2081 of its weight. These crystals are not 

 altered by exposure to the air unless it be very dry. From Mr. 

 Herschell's experiments, this salt appears to be composed of 



2 atoms hyposulphurous acid = 6*000 



1 atom hme = 3*625 



6 atoms water = 6*750 



16*375 



(2.) Hyposulphite of Potash. — This salt ci"ystallizes in a 

 confused mass of spiculee. It has a penetrating taste, like nitre, 

 succeeded by bitterness, and deliquesces speedily when exposed 

 to the air. When heated, it dries down to a white mass, then 

 takes fire, and burns much like a piece of tinder. 



(3.) Hyposulphite of Soda. — It crystallizes in silky tufts 

 radiating from centres, which at length extend through the 

 whole liquid, and become almost solid. Its taste is intensely 

 bitter and nauseous. When heated, it undergoes the watery 

 fusion, then dries into a white mass, and at length takes tire, 

 burning with a vivid deflagration, and a bright-yellow flame. 



(4.) Hyposulphite of Ammonia. — This salt does not easily 

 crystallize regularly. Its taste is bitingly pungent, succeeded by 

 a disgusting-bitterness. When heated, it burns with a weak 

 flame, and evaporates entirely. 



(5.) Hyposulphite of Bur iftcs. — This salt is a white, brilliant, 

 scaly powder, which is soluble in dilute muriatic acid ; but 

 which requires more than 2000 times its weight of water to 

 dissolve it. When heated on platinum foil, it is thrown into a 



