56 



CHEMISTRY. 



Element* 



of 

 ChrmiKry. 



SECT. IV. Tvngstic Acid. 



Tunguic 

 acid. 



Molybdic 

 acid. 



How ob- 

 tained. 



Its proper, 

 tie*. 



The substance originally called tungstic acid, was 

 discovered by Scheelo. It was not pure, being con- 

 taminated by the acid empli yrd in separating it. 



The real tungstic acid is a yellow powder, first 

 described by the Eluyarta. It is tasteless, insoluble 

 in water, and has no effect on vegetable blues. It 

 is rather an oxide than an acid. But it combines 

 with the salifiahle bases, and forms a class of salts 

 called tungslaics. 



SKCT. V. Of Molybdic Acid. 



This acid was discovered by Scheele. It has been 

 Jatcly examined by Bucholz. 



It may be obtained by digesting nitric acid on 

 molybdena, till the whole is converted into a white 

 mass. Edulcorate this mass with water, the residue 

 is molybdic acid. 



It is a white powder of the specific gravity 3.460. 

 In close vessels it melts and crystallizes when heated ; 

 but in open vessels it sublimes, and may be collected 

 in the form of brilliant yellow scales. 



It is soluble in 960 parts of water. The solution 

 is pale yellow. It is tasteless, but reddens vegetable 

 blues. 



Molybdic acid is not affected by oxygen gas j but 

 it is decomposed by sulphur and charcoal, and seve- 

 ral of the metals. 



It combines with the salifiable bases, and forms a 

 class of salts called motybdates. 



It dissolves in sulphuric acid. The solution is co- 

 lourless when hot, but becomes blue when cold. It 

 dissolves also in muriatic acid, but not in nitric acid. 



According to the analysis of Bucholz, it is com- 

 posed of 



67 molybdenum. 

 33 oxygen. 



100 



SECT. VI. Of Chromic Add. 



This acid was discovered by Vauquelin. It may 

 be obtained from the red lead ore of Siberia, by boil- 

 ing the ore with carbonate of soda, decanting off the 

 fluid solution, and saturating it with sulphuric acid. 

 A red powder falls, which is chromic acid. 



It has a red or orange yellow colour, an acrid and 

 metallic taste ; is soluble in water, and crystallizes 

 in elongated prisms of a ruby colour. 



When heated it gives out oxygen gas, and is con- 

 verted into green oxide of chromium. 



When mixed with filings of tin and muriatic acid, 

 it becomes at first yellowish brown, and afterwards 

 assumes a beautiful green colour. When treated with 

 acids, and various other combustibles, a green colour 

 is also evolved. 



SECT. VII. Of Columbic Acid. 



olumbic This acid was discovered by Hatchet in an ore 

 acid. 



Composi- 

 tion. 



Chromic 

 acid. 



How ob- 

 tained. 



lu proper- 

 lie*. 



from America of a black colour, which he found in Elememi 

 the British Museum. It was obtained by fusing the c 

 ore wilh potash, dissolving the potash in \vat<T, and '_ r _ ' _.' 

 adding nitric arid to the solution. The columbic How ol>- 

 acid precipitated in flake!. timed. 



It is a powder of a white colour, and not rery J|g pr0 p cr . 

 heavy. It is tasteless, insoluble in water, but gives t ; es . 

 a red colour to vegetable blues. 



Sulphuric acid dissolves it, and forms a colourless 

 solution, from which the columbic acid is precipita- 

 ted by water. It is soluble also in muriatic acid, but 

 not in nitric acid. 



It combines with the salifiable bases, and forms a 

 class of salts called columbates. 



CLASS III. Combustible Acids. 



The acids belonging to this class may be distin- Combuiti- 

 guished by the following properties. ble acids. 



1. If they be combined with potash, and distilled, Then- pro- 

 they are decomposed, charcoal is usually evolved, and parties. 



a considerable quantity of heavy inflammable air ex- 

 tricated. 



2. All of them contain at least two simple com- 

 bustibles as a base, namely carbon and hydrogen. 

 Some of them also contain azote. Oxygen usually 

 enters into their composition, though not perhaps al- 

 ways. 



3. They do not seem capable of combining with 

 different doses of oxygen. Whenever the proportion 

 of oxygen changes, that of the other constituents 

 varies also. 



4. They are decomposed by the action of the more 

 powerful acid supporters, and either converted into 

 other combustible acids, or into oxide and acid pro- 

 ducts. 



They may be divided into four orders. Those be-' 

 longing to the first crystallize, and may be volatilized 

 without decomposition. Those belonging to the se- 

 cond likewise crystallize, but they cannot be vola- 

 tilized without decomposition. Those belonging to 

 the third order are not crystallizable, though they 

 may be exhibited in the state of a dry mass. Under 

 the fourth order are placed three acids, which, from 

 the singulnrity of their properties, ought to be con- 

 sidered apart. 



The following Table exhibits the names and com- 

 ponent parts of each of these acids, as far as is known 

 at present. 



ORDER I. Crystallizable, volatilizable. 



