Correspondence of M, Van Mans. 145 



vaterof the solution, displaces from the decomposing metal hydro- 

 gen, which approadies llie decomposed salt, to place itself in the 

 room of its equivalent under the form of water, and peculiarly to 

 the water of oxidation of the oxide of this salt, whereby this 

 oxide is reduced, and that the acid adhering to this water is 

 substituted for the iiydrogeii, or takes the place of this principle, 

 and thus forms in every respect the new salt. It is impossible 

 that the case can be otherwise. The metal is not fused, but it 

 is newly composed. It is the action which takes place under 

 the pile, and wherever oxides are reduced without their oxygen 

 being hot enough to pass to another body. When the solution is 

 saturated with salt, the decomposition is slow or null : this is 

 because the metal precipitated has not a free motion : but is this 

 requisite ? I sav no: but free water is requisite for it, and par- 

 ticularly water of solution which is separated from the salt; then 

 it requiries the caloric with which this water is supercomposed. 

 The metals which are oxidated by water are not separated or 

 reduced, and when thev are so thev form no arborescence. 



It has been discovered in Italy, that the tincture of salt of 

 tartar dissolves phosphorus without decomposing it, or forms a 

 liquid phosphuret of its alkali : and caustic lixivium diluted in 

 alcohol operates tlie same solution. Mere we have in the first 

 place the defect of water, and afterwards the affinity of water for 

 alcohol, which hinders the phosphuret from being decomposed 

 as soon as it is formed. But add more water, and particularly 

 warm water, and instantly phosphuretted hydrogen gas appears. 

 The alcohol contracts a very intimate union with the strong al- 

 kalies, and the alcoholate of potash, if not the potassate of alco- 

 hol ; for I thiidc tliat in this union the alcohol acts like an oxide, 

 and tlie potash like an acid, and becomes very intensely hy- 

 drated. I once found large crystals in a very old tinctiu'e of 

 salt of tartar: they were neuter on the vegetable blues : to the 

 lasc thev were at first salt and bitter, and afterwards very corro- 

 sive. In the open air, when I wished to dry them they deli- 

 quesced, giving out a smell of alcohol, and nothing but caustic 

 potash remained. The little diflference between the intensity of 

 tlic alcohol and of the potash, makes this salt be so easily de- 

 comj)osed, i)ut it is hydrated in the ratio of the combined energy 

 of the elements. Its hydrate is already liquid. I have thus ob- 

 tained in a crystalline form oxygenate of potash. This salt was 

 fuiiiished to me by treating caustic potash with red oxide of 

 mercury. 



I have succeeded in depriving ink of its principle of corru])tion 

 by infusing the gall-nuts in common beer vinegar. They are to 

 V)C broken into a loarse powder, a!id infused two or three days in 



Vol. 18. No. 220. Auiiust IfSlti. K a retort 



