B A K 



fcabridif MublfnkrgVu U>1 which we have fpccinicii;. fro.u its 

 fiuder,) an(} radkalts of Schwsgriclie.i's Supplement, may 

 poflibly be likewife varieties of B.fontana. 



BARYTES, ia Chemijhy, one of the earthy fubftances 

 termed alhalwe. We ftated that this earth was confidered 

 hv Bergman, Lavoifier, and other emment chemilts, as a 

 refraao?y metalhc oxyd ; and this fuppofition has been 

 fince confirmed by the experiments of B.rz.ehus and P^ntm, 

 who led by fir H. Davy's decompofition of potalh and 

 foda'by galvanifm, fubjeded this earth to the fame agent. 

 Th<-ir experiments were- ;,liended with complete fucceis, 

 and' have been fince verilled by fir H. Davy and other 

 chemifts. To , his metallic bafis, Davy gave the name oi 

 harlum. Moi.^ lately, Dr. Clarke of Cambridge thought 

 he had decompofed this ea-ih by expofing it to an mtenJe 

 heat produced by the combuftion of a ftream of oxygen 

 and hydrogen gas, mixed together in the requifite propor- 

 tions to form water. To the metal thus obtained, he pro- 

 pofcd to give the name oi phtmhim. Many chemifts, how- 

 ever, think, that Dr. Clarke from fome cauie or other per- 

 mitted himfelf to be deceived in thefe expenments, and that 

 laftead of a metal he only obtained a flag with a pleudo- 

 iRetallic furface. , , 



Barium obtained by galvanic agency is a folid meta^ ot 

 the colour of fii.er. It melts at a temperature below 

 rednefs, and is not volatihzed by a heat capable of melting 

 pkte-glafs ; but at that temperature it ads violently on 

 tlie glafs, probably by decompofing the alkali of the glafs, 

 and converting it into a protoxyd. When expofed to the 

 t\T, it rapidly tarnilhes, abforbs oxygen, and is converted 

 into barytes. It finks readily in water, and feems to be at 

 leaft. four or five times heavier than that fluid. It decom- 

 pofes water very rapidly. Hydrogen is emitted, and the 

 barium is converted into barytes. Barium feems to be 

 both duftile and malleable. 



Barium, according to the experiments of Gay Lullac 

 iAd Thenard, combines with two proportions of oxygen. 

 The protoxyd is the earth called barytes. No direa 

 experiments have been made to afcertain the proportion of 

 oxygen it contains ; but this may be determined by other 

 means. Thus, fulphate of barytes is compofed of 



Sulphuric acid 



Barytes . . - ■ 



and carbonate of barytes of 



Carbonic acid • - - 10° 



Barytes ... - 354-54 



Hence it may be eafily afcertained by calculation, that 

 the equivalent number for barytes is 97.5, oxygen being 10 ; 

 and i? we confider this earth as a protoxyd, the number 

 for barium will of courfe be 97.5 —10 = 87.5. Hence 

 one hundred parts of barytes confift of 



100 

 194 



Barium 

 Oxygen 



89.74 

 10.26 



100.00 



Gay LulTac and Thenard found, that when dry barium, 

 from nitrate of barytes, or from the carbonate of barytes 

 decompofed by "charcoal, was heated in oxygen gas, it 

 abforbed that gas with great rapidity. The peroxyd 

 fbrrtved was grey. It gave out its excefs of oxygen, when 



B A S 



put into water. When heated in hydrogen gas, the hydro- 

 gen was abforbed, and water was formed, which remained 

 united to the barytes. 



The falts of barytes are defcribed under Salts. The 

 equivalent numbers cf thefe, however, require a little cor- 

 reftion ; for which purpofe, we refer our readers to the 

 article Atomic Theory, where the lateft determinations 

 will be found. 



The muriate of barytes (fee Salts) has been employed 

 as a medicine in fcrofulous and cancerous calcs. Al- 

 though it has been accounted highly poifonous, Dr. 

 Johnftone, in his " Effay on Poilons," fays, that he 

 has feen a female take 30 drops of a faturated folution 

 of muriate uf barytes repeatedly in the courfe of a day, 

 without even n.iurea : and he concludes, that it would 

 require at leaft two or three drachms to do mifchief. 

 Barytes is capable of making a very tenacious cement, 

 but it has been yet much ufed in the ai-ts, except by 

 limners, as a molt excellent water-colour. Mr. Hume, 

 fays Mr. Parkes (Chem. Catech,), many years ago dii- 

 covered the method of making a colour from this earth. It 

 is the only 'white for water-painting that never changes. 

 It has another peculiar advantage, that it may be mixed 

 with any other colour without injury. It is fold under the 

 name of " Hume's permanent White." See White. 



Barytes, Carbonate of. See Carbonate oJ Ba- 

 rytes. 



BASALT, in Mineralogy and Geology, a ccmpaft dark- 

 coloured rock, claffed by geologifts vrith trap-rocks. (See 

 Trap.) It has received the name of whin-ftone in the 

 north of England (fee Whin-stone) ; and in Staffordfhire, 

 Rowley -rag (fee Rowlev-rag). In the arrangement 

 of rocks by the Wernerian gcologifts, bafalt is confidered 

 as a compaft green-ftone, which latter rock is compofed of 

 felfpar and hornblende ; but green-ftone being more cryf- 

 talhne, the conftituent parts are diftinftly feparated. Green- 

 ftone and bafalt often pafs into each other. (See Green- 

 Stone, Addenda.) Bafalt has generally been clatfed with 

 fimple minerals ; and a (hort account of its charafters and 

 conftituent parts are given under the article Basalt 

 (which fee). More correft analyfes of this rock have fince 

 been made, in which foda is found to be a conftituent part. 

 We greatly doubt the propriety of clafling bafalt with 

 fimple minerals ; for it has been afcertained, that moft ba- 

 faltic rocks are compofed of two or more minerals inti- 

 mately mixed, but requiring the aid of a lens to diftinguifti 

 them. Of thefe, the mineral called augit is the one which 

 prevails, or forms the dark colour : it is intermixed with 

 felfpar and olivine. It is thus afcertained that bafalt refem- 

 bles in its conftituent parts, as it does in other ch#aaers, 

 dark compadt lava. (See Volcanic ProduHs.) Before 

 the obfervations of the French mineralogift Cordier, botli 

 bafalt and compaft dark lava were fuppofed to be formed 

 of hornblende and felfpar. 



Before the blow-pipe, bafalt melts eafily, without addition, 

 into an opaque black -coloured glafs. It melts at a com 

 parative low degree of temperature from 38° to 45° of 

 Wedgewood. If it be cooled rapidly, the mafs is vitrified ; 

 if cooled flowly, it is ftony, and prefents a tendency to a 

 columnar arrangement. Some interefting experiments of 

 this kind are defcribed under the article Rowley-rag 

 (which fee). 



The conftituent parts of bafalt, as given by Klaproth and 

 Dr. Kennedy, are as follow : 



B«:jlt 



