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ignition, more efpecially when a common wine-glafs is ufed inftead of a jar.

So eafily is this hyperoxymuriat decompofed,that when fimpiy rubbed in a mortar with variouscombuftible bodies, it detonates with them moreor lefs forcibly : this we believe was firft afcer-tained by Mr. Hoyle, k and nearly about thefame time by Vauquelin and Fourcroy. Wefhall felerit fome of the moft ftriking inftances.Half a grain of phofphorus and an equal quantityof the fait, explode ahnoft immediately, with aviolent report and a bright flafli. Two grainsof the fait and I of very finely pulverized anddry charcoal, produce by a fmart ftroke aftrong flame, without much report. Half agrain of dry pit-coal and I grain of fait, pro-duce fparks and confiderable reports. Onegrain of the fait and three-fourths of a grain offulphur, produce one very loud explofion;when the fulphur is reduced to a quarter of agrain, 'there are produced by a long fmartftroke with the peftle, feveral fmall fuccefliveexplofions. One grain of the fait and an equalweight of alkaline fulphuret, produce a veryloud explofion with flame; it is remarkablehowever that this mixture, when melted overthe fire, merely emits a flafli without any report,in which it differs materially from the fulmin-ating powder made with nitre and fulphuret.One grain of white fugar and 2 of the fait,produce a number of fucceflive reports, like .theloud crack of a whip. A fimilar effe£t isoccafioned by rubbing a few grains of the faitwith as many drops of fpermaceti oil, olive oil,and various eflential oils, particularly oil ofturpentine, alfo with camphor, rofin, or indigo.If fulphuric acid is poured on any of the fore-going mixtures previous to detonation, a copiousflame, but without much noife, is emitted. Theloudnefs of the explofion in the above cafes ismaterially influenced by the degree of fridtion,hence if the ingredients, after being thoroughlymixed by flight friftion in the mortar not fuffi-cient to produce decompofition (which may beeffefted in all cafes except when phofphorus isemployed) are then wrapped in a piece of tin-foil, and ftruck on an anvil with a cold andheavy hammer, the violence of the explofionwill be remarkably increafed, and feveral fub-ftances may be thus inflamed, which remainunaltered when fimple fridftion is had recourfet.o ; fuch are cotton wool, certain of the metallicfulphurets, and almoft all the metals.

Hyperoxymuriat of potafh is chiefly ufed inthe laboratory, where it is employed in the pre-

* Manchufter Phil. Trans. V. p 233- *

paration of.the pureft oxygen gas. A fewgrains of it ftirred into an ounce of commonmuriatic acid, form a ufeful extemporaneousbleaching liquor, for various purpofes. It hasbeen attempted in France to compofe a gun-powder of this fait, inftead of nitre, but with-out fuccefs ; the mixture exploded while it wasgrinding, and killed two perfons who wereHanding near.

Hyperoxymuriat of Soda.*

This fait is prepared in the fame manner asthe former, by fubftituting foda for potafh, andwith the fame phenomena. It is very difficultto obtain it pure on account of its folubility inwater being little different from that of muriatof foda. It is foluble in three parts of cold,and fomewhat lefs of boiling water, and isflightly deliquefeent. It is alfo foluble in alco-hol, and appears to render muriat of foda alfofoluble in the fame menftruum. By repeatedfolutions and cryftallizations in alcohol it mayhowever be obtained (though with great diffi-culty) in a ftate of purity. It cryftallizes incubes, and produces a fenfation of cold in themouth. It is decompofable with decompofitionof the acid by the fame fubftances and in thefame manner as the former fpecies. Its bafeis abftra£Ied only by potaffi. It is compofedof 66.2 Hyperoxymuriatic acid

29.6 Soda4.2 Water

100.0

It is made no ufe of.

Hyperoxymuriat of Barytes. 1The earthy hyperoxymuriats are not Co eafilyprepared as the alkaline ores, on account of theinferior affinity fubfifting between their ingredi-ents, and the inferior folubility of the bafes. Toprepare the prefent fait the Woulfe bottlesffiould be charged with pure barytes, diffufediii warm water, and a current of oxymuriaticacid gas fhould be paffed through the liquor tillcompleat faturation. This fait is foluble in fourparts of cold and a quantity of warm water. Itcryftallizes like the muriat of barytes and canonly be obtained pure by boiling the entire liquorwith phofphat of filver diflolved in diftilledvinegar; the muriat of barytes and phofphat offilver mutually decompofe each other, and formtwo infoluble falts, while the hyperoxymuriatis not affedted. This fait has-the fame proper-ties as the preceding, and is compofed of

Chentvix, in Phil. Trans. * Chenevix.