33^ Trocefs for preparing the Weld Yellow, 



add for each pound of whiting three ounces of alum previonfly 

 pulverized tolerably fine. The alum muftbe added gradually, 

 and the operator mould keep furring with his deal flick 

 during the adminiftration; for a double decompaction is 

 effected, accompanied with effervefcencc, and carbonic acid 

 is difcharged. Thus, if the alum were not adminiftered gra- 

 dually, the boiler would overflow with the violence of the ef- 

 fervefcence; and, if the whiting were not well divided previous 

 to the introduction of the alum, the diilribution amongfr. the 

 uniting would be unequal, and the colour would be injured. 

 When the alum is all introduced, and the effervefcence has 

 ceafed, the balls is properly prepared. The fire may be then 

 drawn, and it may remain for any length of time without in- 

 jury, till the other materials are ready. Having thus prepared 

 the bafis, take the welds, place them, with their roots iipper- 

 nio(t,in another copperboiler, pour in foft water enough to cover 

 every part containing feed, and let them boil not more than 

 fifteen minutes: then take them out, place them, with their 

 roots uppermoft, in a tub to catch the liquor which runs from 

 them, and pafs the liquor in the copper, with what runs from 

 the welds in the tub, through a flannel filter, to intercept the 

 feeds and faecula ; and thus the colouring matter is prepared. 



It is impoffible to fay what quantity of welds mould be em- 

 ployed to any given quantity of whiting, for fo'fne bundles 

 will contain three times as much feed as others, It is well, 

 however, to know, that if too much colouring matter be 

 prepared, it may be kept in an earthen or deal veiiel for niany 

 weeks, without fuftaining any injury. 



Having filtered a fufheient quantity of the weld liquor, put 

 a fire under the boiler containing the bafis, and add the weld 

 liquor till the colour be obtained. When fufficient colour- 

 inn- matter is added to the bafis, the fire fhould be railed to a 

 boiling heat, and the work is finifhed. In order to be fatis^ 

 fied when the greateft firength of colour is obtained, for there 

 is a ne plus ultra, take a little out on chalk, which will abforb 

 the moifture inftantly ; when it may be laid on paper with $ 

 brum, and viewed perfectly dry in a few minutes. 



The contents of the furnace Arnold be then put into a deal 

 or earthen veficl to precipitate. The next day the liquor may 

 be poured off, and the colour may be placed on large pieces 

 of chalk, which in a few hours will abforb the moiflure, and 

 it will then be fit for u^c or fate. 



The liquor poured off from the colour may, with the addi- 

 tion of water, be ufed again, and the old welds may be boiled 

 a fecond time, and taken out previous to the addition of heih 

 welds, fo that no colouring matter will be loft. 



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