^o6 jinajyfts of a Mhitral from New Saiilh U^alts. 



None of thcfe fubftances feem to be at all atled upon by the nitrous acid, concentrated or 

 diintetl, nor by oil of vitriol diluted wi,th about equal its meafure of water. In the cold, or 

 in a boiling lieat, the mineral rein^iried unaltered in its appearance, and the acids had ex- 

 trafted nothing from it that could be precipitated by alkali. 



Oil of vitriol boiled upon the mineral to drynefs, as in the procefj of making alum from 

 clay, produced no .ipparcnt change in it ; but a lixivium made from this dry mafs witl» 

 •water, ou being faturated with alkali, became fomewhat turbid, and depofited, exceeding 

 ilowly, a white earth in a gelatinous ftatc, too fmall in quantity foj^any particular examina- 

 tion, but which, from its afpecl, from the manner In which it was obtained, and from the 

 tafte of tlie lixivium before tlie addition of the alkali, was judged to be the aluminous earth. 



The marine acid during digcllion feemtd to have as little a£lion as the other two ; but 

 on pouring in fome water, with a view only to dilute and walh out only the remaining part 

 of the acid, a reiriarkable ililTerence prefented itfelf; the liquor became inftantly white as 

 milk, with a fine white eurdly fubflance intermixed; the ftrong acid having extraded fonie- 

 HhLig which the fimple dilution with water precipitated. 



The white matter being walhed oft", more fpirit of fait was added to the remainder, and 

 •the digeftion repeated with a long tube inferted into the mouth of the glafs, fo as nearly 

 to prevent evaporation. The acid, when cold, and fettled fine, was poured off clear, and 

 ■on diluting it with water the fame milky appearance was produced as at firft. 



The digeftion was repeated feveral times fuccelTively with frelh quantities of the acid, till 

 no milkinefs appeared on dilution. The quantity of mineral employed was 24 grains, and 

 the refiduum, after the operations, waflied and dried, weighed fomewhat ' more than ig 

 grains, fo that about one-fifth of it had been diffolved. In fome parcels of the mineral, 

 taken up promifcuoufly, the proportion of foluble matter was much lefs, and in none 

 greater. It is only the white p-trt, and only a portion of tliis, that the acid appears to a£t 

 upon ; the white fand, much of the wliite foft earth, and all the black particles remai;i 

 unaltered. 



To try whether this tedious procefs of folution could be expedited by triture or calcina- 

 tion, fome of the mineral was rubbed in a mortar j and in doing this, it appeared pretty 

 remarkable, that though the black part bore but an inconfiderable proportion to the reft, 

 yet the whitenefs of the other was foon covered and fupprefled by it ; the whole becoming 

 an uniformly black, fliining, foft, un£luous mafs, like black lead, rubbed in the fame man- 

 gier with a few gritty particles, perceptible on prclTrng hard with the peftle. A penny- 

 weight of this mixed, fpread thin on the bottom of a porcelain vefl'el, was calcined about 

 an hour, with a fire between 30 and 40 degrees * ; it became of an uniform, dull, white or 

 grey colour, excepting a very few, and very fmall, fparkling, black particles, fufpeded to be 

 thofc which had eluded the aftion of the peftle ; it loft in weight fix grains, or one- fourth. 



The mineral thus ground and calcined was found to be juft as dilTicult of folution as in 

 its crude ftate, with this additional difadvantage, that the undiflblved fine particles are in- 

 difpofed to fettle from the liquor. 



• By degrees of firt or heat above igaiiiou, I mean thofe of my thermometer ; ami fome idea may be 

 formed of their value by rccoUefling that they commence at vifible rcdncfs ; and that the extreme llea^of a 

 good air-furnace of the common conftruftion is »69' or a little more. W. 



In 



