308 balard's hesearches concerning the nature of 



cumstances, which I have yet imperfectly ascertained, I have not per- 

 ceived any disengagement of this gas. I shall, however, soon endeavour 

 to supply this hiatus ; for the exact determination of the circumstances 

 may greatly influence the fabrication of chlorate of potash. It is evi- 

 dent that if the conversion into chlorite occurred without the disengage- 

 ment of oxygen, then would be obtained, for a given weight of potash, 

 three times more of this salt than is usually procured. The presence 

 of an excess of base may prevent the decomposition of the chlorites, but 

 this base must be powerful ; oxide of zinc and magnesia are insuffi- 

 ciently so for it. Therefore their chlorites, soon after formation, yield 

 oxygen gas mixed with chlorine if they have an excess of acid, and are 

 converted into chlorates and chlorides. The attempt to obtain these iu 

 a dry state would be fruitless, even when mixed vvitli an excess of oxide, 

 and the evaporation performed by the air-pump. 



The case is different with those with a base of potash, soda, lime, 

 barytes, and strontia. These may be obtained in a solid state by eva- 

 poration in a dry vacuum, or even by distillation at a low temperature ; 

 but for this there must always be a great excess of alkali. But notwith- 

 standing this precaution, it often happens that during this evaporation, 

 even in vacuo, a notable portion of hypochlorite is converted into chlo- 

 rate and chloride. 



The hypochlorites are very readily decomposed by the acids. Al- 

 though hypochlorous acid expels carbonic acid from its combinations, 

 it is in its turn expelled from its own by a current of carbonic acid gas, 

 which shows how weak are its affinities for bases. When the dry hypo- 

 chlorites are pure, they may be used for preparing hypochlorous acid gas, 

 provided they are treated with an acid which contains but little water, 

 — concentrated phosphoric acid for example. But as it is difficult to ob- 

 tain them both dry and free from chlorides and chlorates, and, as in this 

 case, the hypocldorous acid gas is mixed with chlorine, it is better to em- 

 ploy the process which I have already described for preparing it. 



It has already been stated that the decolorizing compounds of chlo- 

 rine have a great disposition to convert sulphur, iodine, phosphorus 

 and arsenic, into sulphuric, iodic, phosphoric, and arsenic acid, which, 

 combining with the oxide of these compounds, give rise to saline com- 

 binations. I have also observed the same property in the hypochlorites. 

 Fragments of arsenic blackened on their surface by a little protoxide, 

 put into a solution of these salts, have their metallic lustre immediately 

 restored, as stated by M. Soubeiran to occur with the chlorides of lime, 

 soda, &c. 



The metals act with the hypochlorites as with the decolorizing com- 

 binations themselves. Gold and platina are not altered. Silver is trans- 

 formed, though slowly, into chloride, with the disengagement of oxygen. 

 Iron is very readily oxidized. As to tin and copper, they readily be- 



