CHEMISTRY. 



Wctnenn the tr constituents, and distilling them together 

 over a moderate fire. It i black and brilliant, and 

 J2l ought to be kept under water. 



Sulphur combine, readily with arsenic by heat. 

 Two distinct compounds of these two bodies arc 

 found native. The first, called realgar, ig of a scar- 

 let colour, and often crystallizes in transparent prisms. 

 It is tasteless, and not nearly so poisonous as arsenic. 

 It it composed of 60 arsenic and 80 sulphur. The 

 second compound is called orpimcnt. It is of a fine 

 yellow colour, and may be formed by pouring a so- 

 lution of sulphureted hydrogen into arsenic dissolved 

 in water. It is foliated, and much heavier than real. 

 gar. According to Thenard, it is composed of three 

 sulphur and four arsenic. 



Alloys. \rsenic does not combine with the simple in- 



rombustibles, but it unites with the metals, and ren- 

 ders them brittle. None of its alloys have been ap- 

 plied to any useful purpose. 



SECT. XX. Of Magannr. 



SECT. XIX. Of Cobalt. 



Colwit. 



Cobalt occurs in different mines in Germany and 

 England, and has been long employed to give a blue 

 colour to glass. Its peculiar properties were first 

 ascertained by Brandt, in 1733. 



Properties. 1. Cobalt has a grey colour, with a shade of red, 

 and is not very brilliant. It is of the hardness of sil- 

 ver, or a little harder. Its specific gravity is 7.7. 

 It is brittle, and easily reduced to powder. It melts 

 at 130 Wedgewood, and crystallizes as it congeals. 

 It is attracted by the magnet, and may itself be con- 

 verted into a magnet. 



2. It is not altered by air nor water at the ordi- 

 nary temperature of the atmosphere, but in a red 

 heat it is gradually converted into an oxide. We are 

 acquainted with 3 oxides of cobalt. 



The protoxide is blue. It may be obtained by 

 dissolving cobalt in nitric acid, precipitating by pot- 

 ash, washing and drying the powder, and exposing 

 it to a red heat for some time. It dissolves in acids 

 without effervescence. It is composed of 83^ co- 

 balt and 16'^ oxygen. 



Moist protoxide, when exposed to the air, gradu- 

 ally absorbs oxygen, and assumes an olive colour. 

 This is the deutoxide of cobalt. When digested in 

 muriatic acid, oxymuriatic acid flies off, and a solu- 

 tion of protoxide is obtained. 



By gradual exposure to the air, more oxygen is 

 absorbed, and the oxide becomes black. This is the 

 peroxide. It forms abundance of oxymuriatic acid 

 gas when digested in muriatic acid. It is composed 

 f 80 cobalt and 20 oxygen. 



3. Cobalt does not combine with carbon or hy- 

 drogen. Snlphuret of cobalt may be formed by 

 melting the metal with sulphuret of potash. It is 

 yellowish white, and is composed of 71.' cobalt and 

 28A sulphur. 



Phosphuret of cobalt may be formed, by throwing 

 bits of phosphorus upon red hot cobalt. It is white 

 and brittle, and soon loses its metallic lustre. 



4. Cobalt does not combine with the simple in- 

 combuatibles. It unites with the different metals, 

 and forms alloys which have been but imperfectly ex- 

 amined. 



-.rnt 



Chrnmirr. 



Ores of the metal called manganese are common, ^T~ 

 in which it occurs always in the state of an oxide. UKtt . 

 Scheele, Bergman, and Gahn, are the chemists to 

 whom we are indebted for the first investigation of 

 its properties. Of late, a valuable set of experi- 

 ments on it have been made by Dr John of Berlin. 



1. Manganese, when pure, is of a greyish white Properties 

 colour, similar to cast iron. Its texture is granular. 

 It is brittle, and rather softer than cast iron, as it 

 may be filed. Its specific gravity is 8.013. 



"2. When exposed to the air, it begins immediate- Ozidrt. 

 ly to absorb oxygen, and soon falls to powder. We 

 are acquainted with three oxides of this metal, dis- 

 tinguished from each other by tlicir colours, namely, 

 the freen, the brntcn, and the black. The protoxide, 

 or green oxide, is formed when manganese is thrown 

 into water. The water is decomposed, and the me- 

 tal assumes the form of a green powder. It is com- 

 posed of 



87 metal. 

 13 oxygen. 



100 



The deutoxide, or brown oxide, is formed by ex- 

 posing the green oxide to the air. It absorbs an ad- 

 ditional dose of oxygen, and assumes a brown co- 

 lour. This oxide is composed of 

 80 metal. 

 'JO oxygen. 



100 



The peroxide, or black oxide, occurs native in 

 great abundance. It may be formed artificially, by 

 dissolving manganese in nitric acid, and evaporating 

 to dryness. It is composed of 



7 1.33 metal. 



28.67 oxygen. 



100.00 



3. Manganese does not combine with hydrogen or 

 carbon, but it unites with phosphorus and sulphur. 



Phosphuret of manganese may be formed by drop- 

 ping phosphorus on red hot manganese. It is white, 

 brittle, granular, and disposed to crystallize. 



Bergman did not succeed in his attempts to com- 

 bine sulphur with manganese. But he formed a sul- 

 phurated oxide, by heating 8 parts of black oxide 

 and 3 parts of sulphur. 



4. Manganese does not combine with the simple 

 incombustibles ; but it unites with the metals, and 

 forms alloys which have been but imperfectly exa- 

 mined. 



SECT. XXI. Of Chromium. 



This metal was discovered by Vauquelin, who ex- Chromium, 

 traded it from the red lead ore of Siberia. Owing to 

 the violent heat necessary to fuse it, its properties are 

 but imperfectly known. 



1. Its colour is white, intermediate between that Properties. 

 of tin and steel. Its specific gravity is 5.90. It is 

 very brittle, assumes a good polish, and is magnetic, 



