54 



CHEMISTRY. 



Compuu- 



liou. 



fluoric 

 acid. 



How ob- 

 tained. 



k$ proper- 

 ties. 



comes somewhat opake when exposed to the air, but 

 doe not attract n.oisture. 



Boiling water docs not dissolve more than 0.02 of 

 this acid, and cold water still i 



Neither oxygen, the simple combustibles, incom- 

 bustibiM, or metals, produce any effect upon this 

 acid. But when heatrd with potaoMum it is decom- 

 posed, and its base Loracium separated. 



From the experiments of Davy, we may conclude 

 that boracic acid is composed of about 33 boracium. 



07 oxygen. 



100 

 It is soluble in alcohol, and alcohol containing it 



burns with a green coloured flame. It dissolves also 



in some of the oils. 



It i: hardly capable of oxidizing any of the metals 



except iron and zinc. 



It combines with the salifiable bases, and forms a 



class of sails called borates. 



SECT. VII. Of Fluoric Acid. 



This acid was discovered by Scheele. He obtain- 

 ed it from a pretty common and beautiful mineral 

 calledy?uor spar, and in this country often Derbyshire 

 spar. This mineral is a compound of fluoric acid 

 and lime. Dr Priestley first obtained the acid in a 

 separate state. 



To procure this acid, pour sulphuric acid on the 

 pounded spar, and apply heat. A gas comes over, 

 which must be received over mercury. It is the acid 

 in question. 



This gas possesses the mechanical properties of air. 

 It does not support combustion, nor can animals 

 breathe it. It smokes when mixed with the atmo- 

 sphere, and has a smell similar to that of muriatic 

 acid. 



It is not altered by exposure to heat or light. 



Water absorbs it rapidly. If glass vessels have 

 been employed to procure it, a jelly is deposited as 

 soon as it comes in contact with the water. This 

 jelly consists of silica, which the gas has dissolved from 

 the glass, and which it held in solution. No me- 

 thod has been yet discovered of obtaining fluoric acid 

 gas free from foreign matter. If leaden vessels be 

 used, the gas does not assume the elastic form, at 

 least we could not procure it by means of these ves- 

 sels. When fluor spar and vitreous boracic acid are 

 heated together, a gas is obtained, which is a combi- 

 nation of the tivo acids, to which Thenard and Gay- 

 Lussac, who discovered this compound gas, have 

 given the name of /iuoboracic acid gas. 



Neither oxygen, the simple combustibles, incom- 

 bustibles, or metals, as far as is known, produce any 

 effect upon this gas. It docs not act powerfully 

 upon the metals. 



The fluoboracic acid is absorbed by water, and 

 forms a very powerful acid liquid, nearly as heavy as 

 sulphuric acid, and capable of resisting as strong a 

 heat before it is volatilized. 



One of the most curious properties of fluoric acid 

 is the ease with which it corrodes glass, when that 

 substance it exposed 19 its fumes. In consequence 



of this property, it has been employed to etch upon 

 glass. 



It combines with the different bases, ai:d forms a CVnurtrr- 

 class of salts called^i/a/M. ""i"" 



All attempts to decompose this acid have failed, 

 in consequence chiefly of the impossibility of making 

 experiments on it in a state of purity. 



CLASS II. Acid Supporter*. 



The acid supporters arc distinguished by the fol- 

 lowing properties : 



1. Thi y cannot be produced by combustion. 

 Hence their base is either a simple incombustible or a 

 metal. 



2. They support combustion. Hence they acidify 

 the combustible bases, and oxidize the metals. 



S. They are decomposed at a high temperature, 

 their oxygen making its escape in the state of gas. 



The oiily acid supporters known at present, are 

 those which have the simple incombustibles and arse- 

 nic for their bases. From analogy, we refer the 

 whole of the metallic acids to this head. 



The followiug Table exhibits a view of all the acid 

 supporters, of their bases, and of the proportion of 

 their constituents, as far as that has been ascertained. 



Acid >up> 

 porter*. 



Their pro- 

 pcrtitt. 



Table of 

 acid sup- 

 porter^ 

 &c. 



Oxygen is an essential constituent of all these acids, 

 as weU as of those belonging to the first class. 



SECT. I. Of Nitric Acid. 



This acid seems to have been first obtained in a ee- Nitric aciA. 

 parate state by Raymond Lully, one of the most ce- 

 lebrated of the alchymittts. It was called at first ma- 

 ter of nitre, aqua/ortis, spirit of nitre. 



It may be obtained, by distilling * mixture of three How ob- 

 parts nitre and one of sulphuric acid in a glass retort, tamed. 



The acid thus obtained has a yellow colour ; but, 

 if kept for a short time in a boiling heat, it becomes 

 colourless. It has a peculiar smell, it smokes when 

 exposed to the atmosphere. Its taste is extremely 

 acid, and it is one of the most corrosive substances 

 known, tinging the skin instantly of an indelible yel- 

 low, and very soon destroying us texture entirely. It iti proper- 

 converts vegetable blues to red. Its specific gravity ties, 

 when strongest never exceeds 1.583. It contains 



