130 



ALUM ALVA. 



sence of a small portion of iron, the Solfatnra alum 

 is not so valuable, for many purposes, as ilial pro- 

 duced elsewhere ; ami, accordingly, it-* u-e is mostly 

 confined to the Neapolitan states. The manufacture 

 of alum directly from its component parts, has, of 

 late years, furnished a large proportion of this sub- 

 stance found in commerce. The process is conducted 

 in the following manner: Sulphur and nitrate of 

 potash (nitre) are mixed together, in the proportions 

 tor forming sulphuric acid, and brought into com- 

 bustion in large leaden chambers, or rooms lined 

 with a thick coating of plaster. The sulphur is thus 

 acidified, and converted into vapour, and, the floor of 

 the apartment being covered with clay of the purest 

 kind, previously calcined, the acid gradually com- 

 bine!) with it, and forms sulphate of alumine, which, 

 after a few days, is dissolved out and considerably 

 reduced by evaporation, when a solution of sulphate 

 of potash (bring the residue of the combustion of the 

 nitre and sulphur) is poured in, and the perfect 

 crystals of alum are deposited. (See Alum-slate and 

 Alum-stone.} The importance of alum in the arts, 

 is \ rry great, and its annual consumption is im- 

 mense. It is employed to increase the hardness of 

 tallow, to remove greasiness from printers' cushions 

 and blocks in calico manufactories, and to render 

 turbid waters limpid. In dyeing, it is used to cleanse 

 and open the pores on the surface of the substance 

 to be dyed, and, by the attraction of the colouring 

 matter for the alumine it contains, to render it fit for 

 receivig the colouring particles. Wood and paper 

 are dipped into a solution of it to render them less 

 combustible. Paper impregnated with alum is use- 

 ful in whitening silver, and in silvering brass without 

 heat. It is also largely used in die composition of 

 crayons, in tannery, and in medicine. 



ALUM, native, is found in most countries, in the 

 state of an efflorescence or mould upon the surface 

 of certain slate clays and lavas, and, in the United 

 States, in mica-slate rocks ; also, in delicate hair- 

 shaped fibres, occupying clefts in a bituminous shale, 

 principally found in Italy. It may always be easily 

 recognised by its sweetish, astringent taste, in which 

 it resembles the artificial alum. It exists only in 

 very limited quantities, and contains too many im- 

 purities to be of any practical use. A native alum 

 has of late been found near the foot of the Andes, 

 in South America, in which soda is substituted for 

 potash. Am. Lyceum, Nat. Hist. New York, vol. 

 iii. p. 19. 



ALCM-SLATE ; a slaty rock, of different degrees 

 of hardness ; colour, greyish, bluish, or iron-black, 

 and often possessed of a glossy or shining lustre. It 

 is chiefly composed of silex and alumine, with vari- 

 able proportions of sulphuret of iron (iron pyrites), 

 lime, bitumen, and magnesia. It is found abun- 

 dantly in most European countries, and from it is 

 obtained the largest part of the alum of commerce. 

 As the alum-slate contains only the remote princi- 

 ples of this salt, the process for obtaining it is some- 

 wliat complicated. In the first place, it is requisite 

 to acidify the sulphur of the pyrites, and combine it 

 with the alumine. This is effected by roasting the 

 ore in contact with the air, and then lixiviating it ; 

 after which, potash is added, and the crystallized 

 alum obtained by evaporation. 



ALUM-STOXE ; a mineral of a greyish or yellow- 

 ish-white colour, fine-grained, and approaching to 

 earthy in its composition, and filled with numerous 

 small cavities. It may be scratched with the knife, 

 and easily reduced to fragments. When strongly 

 heated, it emits a sulphureous gas. It is composed 

 of alumine, 43-92 ; silex, 24OO ; sulphuric acid, 

 25-00 ; potash, 3-08 ; water, 4-00. It is found at 

 Tolfa, in Italy, in secondary rocks, and from it is 



obtained a very pure alum, by simply subjecting it 

 to roasting ami lixiviation. 



ALUMINE, or ALUMINA ; one of the earths enter- 

 ing most largely into the combination of all rocks, 

 clays, and loams. From its forming the plastic 

 principle in clays, it was formerly called argil, or the 

 tirgiflacroiis eurtk ; but since it has been ascertained 

 that it constitutes the have of the salt nlum, it is 

 styled alumine. Like the other earths, it was n- 

 garded as an elementary substance in chemistry, 

 until the researches of Sir II. Davy led to the belief 

 that it was a compound of a peculiar metallic Imse 

 with oxygen. It exists in the state of a hydrate, or 

 in combination with water, in the (iibbsitc, a mineral 

 found in Richmond, Massachusetts, and nearly pure in 

 the corundum gems. The porcelain days ami kaolins 

 contain about half their weight of this earth, lo 

 which they owe their most valuable properties. 

 Alumine may be obtained pure by adding, in the 

 first place, to a solution of alum in twenty parts of 

 water, a small quantity of a solution of carbonate of 

 soda, to precipitate any iron that may be present, 

 and afterwards a little water of ammonia (aipta 

 ammonia:) to the supernatant liquid, separated from 

 its precipitate, which, uniting with the sulphuric 

 acid of the alum, liberates the alumine. On being 

 washed, and thoroughly dried, it is of a white 

 colour, and without taste or smell. It is soluble in 

 liquid soda and potash, from which it may be 

 separated, unaltered, by the acids. It is infusible, 

 except in the heat of the compound blowpipe. 

 Alumine is the basis of porcelain, pottery, bricks, and 

 crucibles. It has a strong affinity for oil anil 

 colouring matter, which causes it to be employed, in 

 the state of days, as a cleansing powder, and, in a 

 state of purity, in the preparation of lakes, in dyeing 

 and calico-printing. It combines with the acids, 

 and forms numerous salts ; the most important of 

 which are the sulphate of alumine and potash (sc<; 

 Alum), and the acetate of alumine. This salt is 

 formed by digesting strong acetic acid (vinrgar) 

 upon the newly-precipitated earth ; but, for the use 

 of the manufacturer, by decomposing alum with 

 acetate of lead, (sugar of lead), or, more economically, 

 with acetate of lime, a gallon of which, of the spe- 

 cific gravity 1-050, is employed for every two and 

 three-quarters pounds of alum. The sulphate of 

 lime formed falls to the bottom, and the acetate of 

 alumine remains in solution with an excess of alum, 

 which is necessary to prevent its decomposition. It 

 is of extensive use in calico-printing and dyeing, as 

 a mordant, and is employed in the place of alum, 

 to which it is generally preferred. 



ALURED, an ancient English annalist, who flour- 

 ished in the beginning of the 12th century, was a. 

 canon and treasurer of the church of St John of 

 Beverley, his native town. His annals come down 

 to his own times in the year 1129, and are valuable 

 both on account of the matter and the manner in 

 which they are written. He is also supposed to be, 

 author of " The History of St John of Beverley,'' 

 a MS. preserved in the Cottonian library. 



ALVA, Ferd. Alvarez, of Toledo, duke of, minister 

 of state, and general of the imperial armies, was born 

 in 1508, of one of the most illustrious families of 

 Spain. He was educated under the eyes of his 

 grandfather, Frederic of Toledo, who instructed 

 him in military and political science. He carried 

 arms, when very young, at the battle of Fa via ; 

 commanded under Charles V. in Hungary ; also at 

 the siege of Tunis, and in the expedition against 

 Algiers. He defended Perpignan again*; th? 

 dauphin, and distinguished himself in Navarre and 

 Catalonia. His cautious character, and his inclina- 

 tion for politics, at first, led men to believe that be 



