Chemical Science. 473 



been removed, consisted of 84.21 selenic acid, and 15.75 water; 

 but it is certain that the selenic acid begins to decompose before it 

 has resi{yned the last portions of water. 



Selenic acid has a powerful attraction for water, and evolves 

 much heat when mixed with it. It is not decomposed by sulphu- 

 retted hydrog^en ; so that the latter body may be used to decom- 

 pose the seleniates of lead and copper. When boiled with muriatic 

 acid it produces selenious acid and chlorine, and the mixture, like 

 aqua reg-ia, will dissolve gold or platina. Selenic acid dissolves 

 zinc alid iron, evolving hydrogen ; it dissolves copper, evolving 

 selenious acid ; and it dissolves gold, but not platina. Sulphurous 

 acid has no action on selenic acid, but instantly decomposes the 

 selenious acid. A solution containing selenic acid is easily decom- 

 posed, by first boiling it with muriatic acid, and then adding 

 sulphurous acid. 



Selenic acid is but little inferior to sulphuric acid in its affinity 

 for bases ; seleniate of baryta is not completely decomposed by 

 sulphuric acid. Its combinations being isomorphous with those 

 of sulphuric acid, and possessing the same crystalline forms, and 

 the same general chemical properties, present but very slight, 

 though very interesting differences from the sulphates. These will 

 be resumed by M. Mitscherlich in a future memoir, with the 

 express object of illustrating the theory of Isomorphism. — Ann. de 

 Chimiey xxxvi. 100. 



14. Preparation of Hyposulphuric Acid. — According to M. 

 Heeren, to obtain the greatest quantity of this acid in the process 

 of passing sulphurous acid over black oxide of manganese, the 

 temperature should be low, and the oxide finely divided. The 

 largest portion of hyposulphuric acid is formed at the commence- 

 ment of the operation. 



15. Singular Habitude of Phosphoric Acid with Alhvmen. — 

 MM. Berzelius and Englehart differed in their results respecting the 

 effect of phosphoric acid on albumen ; the latter found the acid 

 caused precipitation of the substance, the former the reverse. For- 

 tunately coming into company, they made some experiments, and 

 discovered a very singular property of the acid. The acid in Ber- 

 zelius's laboratory not precipitating albumen. Dr. Englehart pre- 

 pared a fresh portion from phosphorus and nitric acid, evaporating 

 the solution in a platina vessel, and heating it to redness. This 

 acid, dissolved in water, precipitated both animal and vegetable 

 albumen abundantly. Another portion of acid, prepared by burn- 

 ing phosphorus in air, also precipitated albumen. After many ex- 

 periments to discover the cause of difference in the acids. Dr. En- 

 glehart remarked, that the two acids lie had prepared, gradually 

 lost their power of precipitating albumen, and in some days were 

 like the acid of Berzelius. This change took place both in open 

 and closed vessels, and was not at all hastened by ebullition. 



