S M A 



S M A 



liil his death, which happened in 17 19, at Chriftchurch, 

 where he was interred, and where, fome years after, a hand- 

 fome monument was erefted to his memory, with an elegant 

 Latin infcription. He left a widow and two children, who 

 were much befriended by the generofity of the princefs of 

 Wales. A colleAion of 6c of his fermons was printed after 

 his death, which foon came to a fecond edition. Biog. 

 Brit. 



SMALT, the laft produce of cobalt, a kind of mineral 

 matter, prepared and purified abroad, and brought hither, 

 fometimes in form of a blue powder, and fometimes in 

 lumps ; chiefly ufed along with (larch, to give linens the 

 finer and clearer cad ; and belt known by the name of 

 powder-blue. See Cobalt. 



The preparation of fmalt, as praftifed in Hermanduria, 

 we iind defcribed in the Philofophical Tranfaftions by Dr. 

 Krieg ; who tells us, that the matter it is made of is the mi- 

 neral (lone called cobalt, or cadmia mineralis ; which being 

 pulverized, and the lighter iluffwafhed away, the remainder 

 is laid on a furnace, and by a fire underneath and afide it, 

 the flames of which are reverberated over it, a matter is fe- 

 parated from it in form of a fmoke ; which, flicking to the 

 walls, makes what we call arfenic. 



When the cobalt has done fmoking, it is cooled, mixed 

 with pot-afhes and powder of white flint-ftones ; the mixture 

 is put in pots, and melted for five or fix hours in a furnace. 

 By this means, the matter is formed into a blue glafs, which 

 being put in cold water, cracks and grows tender ; and is, 

 at length, powdered by an engine, the fineft part feparated 

 by a fieve, put into a mill, and ground in water into a very 

 fine powder ; which, by walhing, is ftill farther feparated 

 from the coarfer, then dried in warm chambers, barrelled 

 up, and fent away. 



There is not a more precarious procefs in all metallurgy 

 than the preparation of this fine blue glafs from cobalt, 

 nor any manufafture in which fo expert workmen are ne- 

 cefTary. The carrying the heat to too great a degree, in the 

 roalling of the cobalt, is a very mifchievous error ; and the 

 fuffering as much of the arfenic as may be to remain in the 

 earth, is greatly to the advantage of the fmalt ; and its co- 

 lour may be greatly heightened by adding common arfenic 

 to it while it is in fufion. 



It is always neceflary to make careful and repeated expe- 

 riments on a new ore, or a kind of cobalt which has not been 

 worked before ; by trying it with various degrees of heat 

 in the roailing, and with different proportions of the flints 

 and pot-afh in the fufion. On comparing the feveral pro- 

 dufts of thefe experiments, it will ealily be feen which yields 

 the fineft colour, and this mull be always after followed in 

 the great operations. 



It is well known, that the beautiful blue glafs, called 

 fmalt, is prepared from the fixed earth of cobalt ; but expe- 

 riments have proved, that this earth alone will not acquire 

 that fine colour. Dr. Link tried fome of it, by keeping 

 it eight hours in the molt intenfe heat ; yet on taking it out, 

 it was only a grey glafs, excepting that there were a few 

 blue fpccks in it near tlie edges of the crucible. Thefe 

 fpecks make no objedlion to this dodlrine, when properly 

 confidered ; for they were owing, doubtlefs, to the fame 

 fubilance which is found necelliry to be ufed, in order to 

 procure the blue colour. 



Flints are the neceflary addition to cobalt for the making 

 of the blue glafs, or fmalt ; and the crucible being made of 

 earth, might eafily contain fome particles of fand. Every 

 piece of fand is a fmall (lone, of the nature of flint ; that 

 is, a piece of cryllal debafed by earth ; and thefe fmall 

 flinta mixing with the glafs of the cobalt earth, while in fu- 



fion, rendered the fmall fpecks, where they were mixed, 

 true fmalt, while the reft remained grey and unaltered. 



This earth of cobalt evidently contains fome portion of 

 copper, though fo fmall in quantity, that it can never be 

 difcemed by the common figns, and fo intimately blended 

 with the earth, that it can never be procured feparate. The 

 lightnefs of this earth alfo, in which the copper refides 

 after the fublimation of the arfenic, is a proof that its 

 quantity muft be very fmall ; yet that it exitts there is evi- 

 dent from the colours it affords. 



Copper is well known to yield a green colour with acids, 

 and a fine blue with alkalies. Thus, a folution of this earth 

 in aqua fortis is of a deep green, and its glafs, when mixed 

 with the alkali of flints and of pot-a(h, is the deep blue 

 fmalt : nor is it wonderful, that the vitrified earth of cobalt 

 will never become blue by calcination alone, fince, if it owes 

 this colour to copper, it cannot be fuppofed to Ihew itfelf 

 till called forth by an alkali. 



Some cobalt yields fmalt before roafting, even better than 

 it would afterwards : this is a peculiar kind of cobalt, but 

 is fo like the relt, that it cannot be dillinguifhed by the 

 eye ; but experiment alone (hews this property in it. 



Though cobalt in general requires roafting, in order to fit 

 it for yielding the fmalt, yet its different kinds require fome 

 more, and fome lefs roailing ; and the degree can never be 

 judged of by the infpeftion of the mineral, but is only 

 known by the experienced artift in the procefs. Hence it is, 

 that expert and inteUigent perfons areneceliary in the fraalt- 

 works more than in almolt any other branch of this fort of 

 bufinefs. 



The addition of a fmall quantity of arfenic, or of the ar- 

 fcnical flowers, during the time that the fmalt is in fufion, 

 adds greatly to the beauty of the colour : this is a praftice 

 kept fecret by the workmen of fome places ; and by this 

 means their fmalt is always rendered better than that of their 

 neighbours. 



It is eafy to fee from this, that the roafting of cobalt is 

 the neceflary beginning of the fmalt-work, not the divelt« 

 ing it of its arfenic, which only happens accidentally in that 

 procefs ; and it would be much better if it did not happen, 

 fince we find the arfenic added afterwards exalts the colour. 

 From hence it is evident, that thofe cobalts which will make 

 fmalt without previous roalling, mull, as they are found to 

 do, make the very fineft fmalt, becaufe their arfenic is yet 

 left in them in great part ; and from this alfo appears the 

 neceflity of having expert workmen for the fmalt-making ; 

 fince the knowing the degree of fire neceflary to the ore is a 

 mofl efRntial article, and after the roafting has been carried 

 to a fufficient degree, every moment's heat diverting it 

 of more of its arfenic than was neceflary, makes the co- 

 lour of the fmalt to be made afterward; fo much the worfe. 

 From this alfo appears the reafon why the blue, made by 

 precipitation from a folution of cobalt, is fo much fupcrior 

 to the common fmalt made by fire ; becaufe in this the arfe- 

 nic is all prefcrved, whereas, in the common way of pre- 

 paring it by fire, it is driven off. Philof. Tranf. N° 396. 

 See Azure and Zai'fuk. 



SMAMLEVO, in Geography, a town of Ruflia, in 

 the government of Viatka, on the Kama; 16 miles S. of 

 Sarapul. 



SMARA, a name of Kama, the Hindoo cupid. (See 

 Kama. ) Smara means the ideal, and in the fanciful mytho- 

 logy of the Eafl, is the reputed fon of Maya, or illufion. 

 See Maya. 



SMARAGD, rTfxi(xy^oc, a precious ilonc of a green 

 colour, very beautiful and brilliant ; called alfo the emerald ; 

 which fee. See alfo G£Mti. 



SMAKAGDUS 



