( 45 ) [Aug. 1, 



PROCEEDINGS OF LEARNED SOCIETIES. 



SOCIETY inf.ituted at t.ondoN for the 



tNCOUP.AGiMENT cf AV.1S, ^!A^)U- 



FACTURES, aWcOMMEacfc. 

 CHEM.SrP.Y. 



THIS fociety have adjudged to Sir H, 

 C. Englefikld, Bart, the gold 

 roetlal for his dilloveiy of a lake hom 

 madiier, the merits of which have been 

 ctrtifitd hy MtfTrs. Weft, Trumbull, 

 Opie, Turner, Daniel and Hoppner. 

 The worthy Baronet has laid before the 

 fociety an account of fcvtra! pr.-iceI1"es, the 

 beft of which may be thus delViibed : 



Enclofe two ounces troy weiglit of the 

 finelt Dutch madder, called crop madder, 

 in a calico bag, capable of containing 

 three or four times that quantity. Put it 

 into a marble mortar, and pour upon it a 

 pint of cold loft water. Pound the mad- 

 iter a.s much as may be w ithout endanger- 

 ing the 43ag: repeat the fame operation 

 with fio* feparaie pin^s of <va er, by 

 which the whole colour of the root will be 

 extrafled, and the refidual root will not be 

 found, when dried, to weigh more than 

 five drachms, apothecaries weight. 



The water loaded with the colouring 

 ihatter, muft be put into an canhen, cr 

 well-tinned copper, or filver veffd, and 

 heated till it juii boils. It mu.'t be then 

 poured into an earthen vcfTel, and an ounce 

 troy weiglit of alum difi'^lved in about a 

 pint of boiling foft water muff be poured 

 into it, and (lined U' til jt is thoroughly 

 mixed. About an our:ce and a half of a 

 faturated folution of mild vegetable alkali 

 fhould be g-ntiy poured in, ftirring the 

 wdiole well all the time. - A ccnfider.ible 

 effervefcence will take place, and an imme- 

 diate precipitation ol the colour. Tbe 

 whole fliould be fuffered to ftand till cdd, 

 and the clear yellow colour may then be 

 poured off from the red precipitate. A 

 quart of boiling fcft water flinildagriin he 

 poured on it, and well ftirred. When 

 CO 1, the colour may be frpar.ted from 

 the liquor by filtration though the paper 

 in the uiual way ; and boiling w.ater 

 fiiould be poured on it in (he filter, till it 

 pafTes through of a light ftraw colour, and 

 quite fiee from any alkaline tiil^e. The 

 colour may now be gently dried, and it 

 will be found to weigh half an ounce, 

 one fourth part of the weight of the mad- 

 der employed. 



By anal)fis, this coI<Tur pofTefTes rather 

 more than 40 per cent, of alnmine. If 

 lei's than an ounce of alum be employed 



with two ounces of madder, the colour 

 will be deeper; but if lei's than thiee 

 quartets of an ounce be ufed, the whole of 

 the colouring matter will not be combined 

 with aluinine ; fo that one ou»ce of aluiii 

 to two ounces of madder feems to be thi 

 beft proportion. 



The gold medal was awarded to Dr. 

 DvcE, of Aberdeen, for his difcovery of 

 a mine of manganefe, which is ftated by 

 ieveral certificates to be equal to that ei- 

 tlier from Devcnlhire or Arnerica, or to 

 what fells in London at about lol. per 

 ton. 



This mine contains a very fine vein of 

 manganel'e cf immenfe- extent, which 

 yieliJ'! .'o the labour of twelve men twenty 

 tons per wptk. The btd of veins feems 

 to run through a large trait of country, 

 extending feven or eight miles in the dl- 

 rc'flion from (buth to north, commencing 

 at he banks of the Don, and proceeds ir« 

 that line to the Tea, vvhcre it is found in 

 the form of block, fand, and fomefimes in 

 pretty f^ilid n'.aiTcs. TiTat in the form of 

 fa'ul, thougli urdit forbkach'mg, may be of 

 great advantage in the manufaflure of 

 eaithen waro and glafs. It is known that 

 the metallic oxides afford all the beautiful 

 variety of colour to be perceived on ena- 

 melled articlefi, as well as the difFcrent 

 tinges of glafs msntifaflured at different 

 places,, ('uc:i tinges being acquired by fame 

 metallic particles mixed in the fand of 

 which the glal's is compofed. By the ad- 

 dition ot a !mal! quantity of puie oxide of 

 mang:u)i'rc to the glafs infufion, it becomes 

 colourltfj ; a little mote give- it a violet 

 or purple colour, and a liuie nvre renders 

 it quite blick. Now, Dr. Dyce conceives, 

 that if a due pr portion of the black find, 

 with that of the other two articles, were 

 melted togethei, a very fine and cheap 

 gla!'* might bemade with lels trouble than 

 by the method niw praitifcd. 



Dr. Dyce has deicribed a method of 

 feparati'.p, the puie from the bafe metals, 

 w ;ich I* bv mixing twopartsof powdered 

 minganefc, with the compound metal, 

 broken into finall pieces for the convcni- 

 tiice of putting the whole into a crucible, 

 which is kept in a fufiicient heat for a 

 (liort time. The wh: le is converted into 

 a biownifh powder, which is then to be 

 mixeii with an equal proportion of pow- 

 dered glal's, and iubmitted to a heat which 

 wiU fule it, when the perfect metals are 

 found at the bottom in a (late of extreme 

 purity. 



