372 CHLORINE. 



rine and oxygen of 3 equivalents of chlorous acid being evolved 

 in a state of mixture and not of combination ; the saline residue 

 consists of 3 equivalents of nitrate and 1 of hyperchlorate of 

 potash, which may be separated by dissolving them in the 

 smallest adequate quantity of boiling water. On cooling, the 

 hyperchlorate separates in small shining crystals, which may be 

 dissolved a second time to obtain them perfectly pure. 



Hyperchloric acid may be prepared from this salt by boiling 

 it with an excess of fluosilicic acid, which forms, with potash, a 

 salt nearly insoluble. After cooling, the clear liquid is decanted 

 and evaporated by a water bath. To eliminate a small excess 

 of hydrofluoric acid, a little silica in fine powder is added to the 

 liquid, which at a certain degree of concentration carries off the 

 former as fluosilicic acid. After being still further concentrated, 

 the acid liquid may be distilled in a retort by a sandbath heat. A 

 very dilute acid comes over first, but the temperature of ebulli- 

 tion rises till it attains 392, after which the receiver should be 

 changed, because what then passes over is a concentrated acid 

 ofsp.gr. 1.65. This acid is a colourless liquid which fumes 

 slightly in the air. It may be still farther concentrated by dis- 

 tilling it with 4 or 5 times its weight of strong sulphuric acid, 

 when the greater part of it is decomposed into chlorine and 

 oxygen, but a portion condenses in a mass of small crystals, 

 and also in long four-sided prismatic needles terminated by 

 dihedral summits, which according to Serullas are two different 

 hydrates of the acid, the last containing least water and being 

 most volatile. The crystals and the concentrated solution of 

 the acid have a great affinity for water ; the acid itself appears 

 not to be isolable. 



The hyperchloric acid is much the most stable of the oxides 

 of chlorine ; it does not bleach, is not altered by the presence of 

 sulphuric acid, and is not decomposed by sulphurous acid or 

 by sulphuretted hydrogen. It dissolves zinc and iron with 

 effervescence, and in point of affinity, is one of the most pow- 

 erful acids. Hyperchloric acid is recognized by producing, 

 with potash, a salt of the same sparing solubility as bitartrate 

 of potash. It is an interesting acid from its composition, and 

 as being the most accessible of the small class containing 

 hyperiodic and hypermanganic acids, to which it belongs. The 

 alkaline hyperchlorates emit much oxygen, when heated, and 

 leave metallic chlorides ; they do not deflagrate so powerfully 

 with combustibles as the chlorates. 



