ALU 



dry (late. What had formerly been confidered as dry car- 

 bonate of alumina is a triple compound of alumina, carbonic 

 acid, and the alkali employed in precipitating the alumina. 



Phofphate of Alumina. This fait may be formed by fatu- 

 rating phofphoric acid with alumina. According to Four- 

 CToy, who is the only chemift that has examined it, the phof- 

 phate of alumina is a taftelefs powder, infoluble in water. 

 When diffolved in excefs of phofphoric acid, it yields a 

 gritty powder and a gummy folution, which by heat is 

 converted into a tranfparent glafs. 



Sulphate of Alumina. See Alum and Sulphate of 

 Alumina. In addition to what has been faid under thefe 

 articles, we may add the following analyfis of alum by 

 Vauquelin, Thenard and Roard, and Berzehus. 



The analyfis of Berzelius is probably moft accurate, and 

 is equivalent to 



Sulphate of alumina - - - 36-85 

 Sulphate of potafh - - - 18.15 



Water 45.00 



Which nearly coincides, according to Dr. Thomfon, with 

 three atoms of fulphate of alumina, one atom of fulphate of 

 potafh, and twenty-three atoms of water. 



According to the experiments of Thenard and Roard, 

 alum ufually contains a little fulphate of iron, and the good- 

 aefs of its qualities as a mordant in dyeing, according to 

 thefe chemifts, depends entirely upon the proportion of that 

 fait prefent. The more free it is from it the better. The 

 pureft alum examined contained about ^^'g^th part of its 

 weight of fulphate of iron ; the irapureil about ts'cc- When 

 freed from fulphate of iron, every fpecies of alum tried afts 

 exaftly in the fame manner as a mordant. 



Sulphite of Alumina. See Sulphite of Alumina. 



Borate of Alumina. This fait may be formed by mixing 

 together the folutions of borate of foda and fulphate of 

 alumina. It is faid to be fcarcely foluble in water. 



Arfeniate of Alumina. See Arskniate of Alumina. 



Tungflate of Alumina. A white powder infoluble in water. 



Acetate of Alumina. See AcETATE of Alumina. 



Benzoate of Alumina. This fait cryftallizes, is foluble in 

 water, and deliquefces on expofure to the air. 



Succinate of Alumina. Wenzel ftates, that this fait cryf- 

 tallizes in prifms, and is eafily decompofed by heat. 



Camphorate of Alumina. This fait may be formed by 

 heating together newly precipitated alumina and camphoric 

 acid. It is a white powder, of an acid bitterifh tafte, and 

 nightly aftringent. Water diflblves about -j-rigth part of its 

 weight of this fait : it is not foluble in boiling water, but 

 feparates as the water cools. Cold alcohol diffolves very 

 little of it ; but by the affiftance of heat that fluid takes up a 

 confiderable quantity, which feparates on the cooling of the 

 alcohol. This fait undergoes but little change from the 

 aftion of the air. Expofed to heat the acid volatilizes ; and 

 when the fait is thrown on burning coals it takes fire, and 

 burns with a blue flame. 



A M A 



Suberate of Alumina. This fait does not cryftallize. It- 

 has a yellowifli colour, and always contains an excefs of 

 acid. On expofure to the air it attrafts moifture. When 

 heated the acid is volatilized, and the alumina left in a (late 

 of purity. 



Oxalate of Alumina. Oxalic acid readily diflblves alumina, 

 and forms an uncryftallizable deliquefcent fait, with excefs 

 of acid, of a yellowifli colour, and fparingly foluble in 

 alcohol. It is faid to be compofed of 



Oxalic acid and water - 

 Alumma - - - 



56 



44 



100 



Mellate of Alumina, This fait exifts in the form of a 

 white flaky powder. 



Tartrate of Alumina. See Tartkates. 



Tartrate of Potajh and Alumina. Tliis triple fait may be 

 formed by faturating tartar with alumina. It nearly re- 

 femblcs the laft; fait. Neither the alkalies nor alkaUne car- 

 bonates, according to Thenard, produce precipitates in this 

 fait. 



Sacla&ate of Alumina. A white powder, infoluble in 

 water. 



Urate of Alumina. A white powder, clofely refembling 

 in its appearance the uric acid. 



Malate of Alumina. This fait is almofl infoluble in 

 water ; hence Mr. Chenevix has propofed the malic acid as a 

 means of feparating alumina from magneiia. 



Sorbate of Alumina. From the experiments of Mr. 

 Donovan, the difcoverer of forbic acid, it appears that this 

 fait has no exifl:ence. 



Zuniate of Alumina. A gummy mafs, not altered by 

 expofure to the air. 



Gallate of Alumina. According to fir Humphrey Davy, 

 a folution of galls, in which alumina has been diff"ufed, 

 depofits after fome time tranfparent prifmatic cryllals, which 

 are the fupcr-gallate of alumina. The quantity of alumina 

 they contain is fo fmall as not to difguile the properties of 

 the acid. 



Dr. Thomfon is difpofed to confider the falts of alumina 

 in general as compofed of one atom of alumina and one atom 

 of the refpeftive acids, and if this be admitted their compofi- 

 tion may be readily afcertained. 



With refpeft to the ufes of the falts of alumina, fee 

 Alum, Dyeing, Mop.dant, Tawing, &c. 



ALUMINITE. See Mineralogy, Addenda. 



ALUMINUM, in Cheniijlry, the metallic bafis of alumina. 

 Sir Humphrey Davy fliewed, that when potaflium is pafled, 

 through alumina heated to whitenefs, a confiderable pro- 

 portion of it is converted into potafli, and grey metallic par- 

 ticles are perceived in the mafs, which effervefce in water and 

 air, and are converted into alumina. When a globule of iron 

 is fufed by galvanifm in contaft with moift alumina, it forms 

 an alloy with aluminum, which effervefces flowly in water, 

 and becomes covered with a white powder. Thefe metallic 

 particles Davy confidered as the bafis of alumina, and in 

 conformity to this view denominated it aluminum. The 

 above, however, is all we know at prefent refpedling this 

 metal. 



ALYXIA, in Botany, (fee Gynopocon,) which latter 

 will probably give way, as in fuch a cafe it ought, being 

 founded in error, to the former. Brown Prodr. Nov. Holl. 

 V. I. 469. 



AMADAN. Add — The prefent town contains in 10,000 

 meanly-built houfes more than 40,000 inhabitants. It is 



famous 



