MANUFACTURES.

421

^tur' faC " Prince's metal .. 4 copper + 2 zinc.

^ _. British tutania. . 4 copper + 4 tin + bismuth 4- 4

regulus of antimony to be com-bined with melted tin at dis-cretion.

Ditto.. . 16 copper + 16 tin + 32 regulus of

antimony.

Queen’s metal . .9 tin + 1 bismuth + 1 anlimony + 1lead or 100 tin +8 regulus anti-mony + bismuth -f 4 copper.

White metal_10 lead + 6 bismuth + 4 regulus

antimony or 10 tin + 8 brass+ 2 regulus antimony.

Hard white ditto, 2 brass + 3 z ’ nc + 10 tin.

Blanched copper, 16 copper+1 neutral arsenical salt.

Printer's types . . 10 lead + 2 antimony.

Small type and 4 9 lead + 2 antimony-pi bismuthstereotype plates. J or 16 lead + 4 antimony +1 tin.

Common pewter.7 tin + 1 lead + | copper -(- ^ zinc.

Hard pewter .. .12 tin + 1 regulus antimony + icopper.

Best pewter .... 100 tin + 17 regulus antimony.

Solder common .2 lead + 1 tj u -

Ditto soft.1 lead + 2 tin.

Do.forsteel joints.19 silver -f- 1 copper 4- 2 brass.

Ditto silver.19 silver + 1 copper 4- 10 brass.

Ditto for plating. 1 brass + 2 silver.

Ditto gold. . . . .12 pure gold+ 2 silver+ 4 copper.

Standard silver. .37 silver + 3 copper.

Ditto gold .II gold + 1 copper.

Jewellery gold . . 8-| copper + 4 silver -j- 1 gold.

Common gold . .3 copper + 1 old brass -f- -f tin.

Menbeim gold . .7 copper + 3 brass + 14 tin.

Gilding inetal.. .4 copper 4- 1 brass + 3£ tin.

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Works for the Production of Acids, Sails, Pigments ,and other Substances.

Alum. Works.

(597.) The saline substance denominated alum by theModerns is found by analysis to consist of

Sulphuric acid.

Alumina.

Potash. .c’nn

100.00

or , according to the atomic theory,

Sulphuric acid 4 -j-alumina 3 -f- soda 1 -j- water 25.

It is of extensive use in the Arts, particularly in dyeing,printing, and medicine.

This is not, however, the same substance which passedunder the name of alum with the Ancients, the latterhaving been merely a vitriolic earth, formed naturally insome mines. Both alum and vitriol are neutral salts orsaline substances, strongly resembling each other. Bothcontain the same acid; both have’ strong astringentqualities; they are both also frequently found in the sameplace, and obtained from the same mineral, and they°*h may be applied in the same manner and for likepurposes. The difference is that vitriol is combinedw, tn a metallic earth, and alum with that of a whitecalled, therefore, alum earth.

The alum of the Ancients was a natural formation,

aT1 v WC ’ accordin gly, find no account of alum and vitriolworks in any Greek or Roman author, except what ismentioned by Pliny , who states that blue vitriol was

voi,. VII,

made in Spain by the process of boiling; and this cir- Mechanicalcumstance he considers as the only one of its kind, and 4>ro ‘ :e33es ',so singular, that he was of opinion no other salt could vbe obtained in the same manner. Besides, every thingrelated by the Ancients of their alum agrees perfectlywith natural vitriolic substances ; but to describe themall might be difficult; for they do not speak of pure crys-tals, but of saline bodies, which Nature herself exhibitsin various ways, and under a variety of forms; andevery small difference in the colour, the exterior or inte-rior conformation, however accidental, provided it couldbe clearly distinguished, was to them sufficient to makea distinct species, and to induce them to give it a newname.

The celebrity which the ancient alum had, as a sub-stance extremely useful in dyeing and medicine, was en-tirely forgotten when the alum of the Moderns becameknown ; but this celebrity was again revived when itwas discovered that real alum could be made fromvitriolic minerals, or that where the latter are foundthere are generally minerals which abound with it.

In many of these places alum works have, in thecourse of time, been erected ; and this circumstance hasserved in some measure to give rise to the opinion thatthe alum of the Ancients and that of the Moderns are thesame salt; because, where the former was found in an-cient times, the latter has since been procured by achemical process.

(598.) The first invention of the process of procuring Formationthe modern alum by artificial means is not known, but itappears to have originated in the East some time soonafter the Xllth Century. In the XVth Century therewere alum works in the neighbourhood of Constantino­ ple , and about that period such works appear to havebeen first introduced into Italy and other Countries ofEurope . The celebrated alum works of Tolfa, about at Tolfa,six miles from Civita Vecchia , in the territories of thePope, are stated by some Italian authors to be the firstworks of the kind established in Europe ; and howeverthis may be, they are the oldest carried on at present.

Here the ore is blown up with gunpowder: it isseparated from the pieces of the rock that adhere to it; itis calcined in furnaces, nearly in the same manner as limeis burned ; in six or seven hours being sufficiently cal-cined and friable, it is then taken out, and laid on pave-ments of a long shape, surrounded with walled trenches;on these it is laid in heaps of a moderate height, whichare watered for forty days with water from the trenches.

The ore being thus decomposed, it is boiled in largecaldrons, and when the water is saturated to. a certainpoint, it is poured into the crystallizing pans, where,after it is cold, it deposits the alum in large crystallinemasses.

At Solfa terra, near Puzzuola, the alum is obtained at Solfa by a different process, Nature herself assisting materially erra ‘in the operation. Sulphurous fumes and sulphuric acidare continually issuing from little crevices in the volcanicsoil of this place, the former of which deposit a concretesulphur; the second gradually penetrates the ancientlavas, which are of an argillaceous nature, combineswith their alumina, and thus forms an alum ore, whichafterwards affords, by lixiviation and crystallization, avery pure alum. .

The first alum works in England were established atWhitby in Yorkshire , by Sir lhomas Chaloner, whowas excommunicated by Pope Pius II. for so doing, hisHoliness having assumed the right, of exclusively sup-3 i