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and a proportional quantity of fulphat of fodaproduced; the latter fait was decompofed bythe combination of chalk and charcoal (in theway defcribed under the article Muriat of Soda ,p. 130) and a quantity of carbonat of foda wasproduced, but probably owing to not employingchalk enough, part of the fulphat of fodaeicaped entire decompofition, and was con-verted by the charcoal into a fulphuret, whichby lixiviation became a hydro-fulphuret, and■ crvftallifed by repofe.

Hydro-fulphuret of foda is ufefully employedas a chemical teft to feparate certain metalsfrom mixed folutions of metals and earths, asthe alkaline hydro-fulphurets will precipitatethe former but not the latter, except thofe ofalumine.

Hydro-fulphuret of Ammonia. The compleatcondenfation of fulphuretted hydrogen and am-moniacal gas, confined over mercury, has beenalready mentioned. The refult is hydro-ful-phuret of ammonia, which however is formedmore conveniently by palling the gas through.liquid ammonia till the latter is faturated.This folution has a greenilh yellow colour, andagrees with the other hydro-fulphurets in theelfential quality of giving out fulphuretted hy-drogen on the addition of an acid, and of notprecipitating any fulphur in the procefs. Whenthe ammonia is in excefs, and the folution con-centrated, it conftantly fends forth white fumeswhen expofed to air, which .confift of .unfatur-ated ammoniacal gas holding hydro-fulphuretof ammonia in folution. This fuming propertywas .firft obferved by Boyle, in the liquor pre-pared by diltilling lime, fal ammoniac, and ful-phur, and which will be afterwards defcribedunder the head of Sulphuretted hydro-fulphurets.

Hydro-fulphuret of Barytes . This fait mightdoubtlefs be prepared like the other hydro-ful-phurets, limply by faturating barytic waterwith fulphuretted hydrogen ; but it is moreconveniently obtained, as Berthollet has diico-vered, through the intermedium of the dry ful-phuret of barytes. For this purpofe mix ful-phat of barytes with about a fixth of its weightof finely powdered charcoal, and calcine it in amoderate red heat for about half an hour, in acovered earthen crucible. This produces afulphuret of barytes which is to be difi'olved tofaturation in boiling water, and on hally eva-poration and cooling a copious quantity of irre-gular cryftalswiil be formed, which may be fe-parated from the adhering liquor by preflingthem between folds of filtering paper, 'lhefait is then white and tranfparent, and is the

hydro-fulphuret of barytes. The folution thatremains is the fame fait with an excefs of ful-phur. If the firli folution before the feparationof the laline cryltals be decompofed by carbon-ated foda, carbonat of barytes falls down, andthe folution contains very pure hydro-fulphuretof foda. If muriatic acid be added inftead ofcarbonated foda, a moll copious emiffion offulphuretted hydrogen takes place, and muri-ated barytes remains in folution. The abovemethods of procuring carbonat and muriat ofbarytes are very ufeful in the laboratory.

Sulphuret of barytes gives out a greaterquantity of fulphuretted hydrogen than anyother of the fulphurets, whence the eale withwhich that portion of the earth becomes fatu-rated with the fulphuretted hydrogen, whichfeparates in the cryftalliue form. This is ex-plained by Berthollet from the ftrong affinitywhich barytes has with fulphuric acid, and theconfequent rapidity with which this acid is ge-generated. Hydro-fulphuret of barytes has anacrid and fulphureous tafte, and is readily de-compofed by the atmofphere, and fulphat ofbarytes is precipitated along with fulphur.

Hydro-fulphuret of Strontian. This fait isformed precifely in the fame way as the former.The gas which it gives out when decompofedby acids burns with a red flame like the otherfalts of ftrontian.

Hydro-fulphuret of Magnefia. If pure mag-nefia is dift'ufed through water, and fulphurettedhydrogen pafled through, a folution is effected,and a hydro-fulphuret of magnefia is formed.

Hydro-fulphuret of Lime. This fait is ob-tained by palling fulphuretted hydrogen throughlime diffufed in water. A ftrong yellow folu-tion is made which, when poured off - clearfrom the remaining lime, fhould be fully fatu-rated with the gas, and the excefs, if any, after-wards expelled by boiling. This folution ha3not been cryftallized.

Berthollet , to whom we are indebted for themoft accurate ideas and experiments on the hy-dro-fulphurets, afligns to barytes the firft rankin the order of affinities of the refpeftive alka-line and earthy bafes to fulphuretted hydrogen.As potafh precipitates lime from the hydro-ful-phuret of lime, it precedes lime in affinity, andlime precipitates and decompofes the hydro-ful-phurets of ammonia and magnefia. The order ofaffinity therefore is, probably, barytes, ftron-tian, potafti, foda, lime, ammonia, and magnefia,the two latter nearly equally. When an alkalinehydro-fulphuret is added to any earthy fait,{thofe of alumine and zircon excepted) no preci-