CHEMISTRY. 



55 



Klemeutt 

 of 



Chemistry. 



Table of the 

 strength 

 and boil- 

 ing point 

 of nitric 

 acid. 



mixed with it a considerable portion of water, from 

 which it cannot be freed. When strongest, this wa- 

 ter amounts to about one-fifth of the whole. 



The following Table, by Mr Dalton, exhibits the 

 strength and boiling point of this acid when of vari- 

 ous densities. 



When of the specific gravity l.i'2 it boils at 248, 

 and may be distilled over without alteration. When 

 cooled sufficiently it congeals, and the freezing point 

 varies exceedingly according to the strength of the 

 acid. There ia a certain strength at which it con- 

 geals most easily, and, if it be either stronger or 

 weaker, the free/ing point is considerably lower. 



Oxygen has no effect upon this acid; but all the 

 simple combustibles decompose it. When poured 

 upon charcoal, phosphorus, or sulphur, at a high 

 temperature, it sets them on fire. When diluted, it 

 effervesces with these bodies, and acidifies them. Hy- 

 drogen gas does not act upon it at the common tem- 

 perature of the atmosphere, but when passed with 

 it through a red hot tube, it detonates, water is 

 formed, and azotic gas disengaged. Boracium is 

 readily converted by it into boracic acid. When 

 poured upon the volatile oils, and even upon several 

 of the fixed oils, it sets them on fire. If it be pre- 

 viously mixed with a little sulphuric acid, it sets al- 

 most ail the oils on fire. 



Azote has no action on this acid, but muriatic 

 acid forms with it the compound called aqua regia, 

 or nitro-murialic acid. 



It is capable of oxidizing all the metals, except 

 gold, platinum, and titanium. With most of the 

 oxides it combines, though some, as the peroxides of 

 tin and antimony, are insoluble in it. It even sets 

 lire to some of the metals, when poured upon them 

 in fusion. 



It absorbs nitrous gas in great abundance, and be- 

 comes first yellow, then orange, then olive, and at 

 last green, according to the proportion of gas pre- 

 sent. Acid thus contaminated with nitrous gas was 

 formerly called depfilogisticated nitric acid, and ni- 

 trous acid ; on the supposition that it was nitric acid 

 deprived of a portion of its oxygen. When fully 



saturated with nitrous gas, it assumes a gaseous state, Elements 

 and is known by the name of gaseous vapour. 



Nitric acid combines with the different salifiable ^"^7- 

 bases, and forms a class of salts called nitrates. 



It has been ascertained, that this acid is a com- Composi- 

 pound of oxygen and azote in the following propor- tion. 

 tions. 



29.77 azote. 

 70.23 oxygen. 



100.00 



SECT. II. Of Nitrous Acid. 



W r hen nitre, which is a compound of nitric acid Nitru$ 

 and potash, is exposed to a red heat, it yields a con- acid, 

 siderable portion of oxygen gas. If the process be. 

 conducted with the proper precautions, and stopped 

 in time, the nitre still retains the properties of a neu- 

 tral salt. But the acid which it contains is obviously 

 in a different state, since it has lost a considerable 

 part of its oxygen. To this new state the term ni- 

 trous acid is applied. 



In this state it was discovered by Scheele, but all 

 attempts to obtain the acid by itself have failed. It 

 is decomposed apparently whenever it is separated 

 frcm the potash \ for fumes of nitrous gas immedi- 

 ately make their appearance. 



SECT. III. Of Arsenic Acid. 



This acid was discovered by Scheele. It may be Arenic 

 formed in the following manner : Mix in a retort one ac * < '- 

 part of muriatic acid, four pans of white oxide of 

 arsenic, and 12 parts of nitric acid of the specific 

 gravity 1.25. Boil the mixture till the oxide disap- How ob- 

 pear, and nitrous fumes cease to be disengaged ; then taiued. 

 evaporate to dryness, and expose the mass to a low 

 red heat. The matter thus obtained is solid arsenic 

 acid, 



It is a white solid mass nearly tasteless, of the spe- its proper- 

 cific gravity 3.391. It is very fixed. It melts at a ties, 

 red heat, and is converted into glass. 



It dissolves slowly in cold, but rapidly in hot wa- 

 ter, and by cautious evaporation may be obtained in 

 crystals. The taste of the solution is acid, caustic, 

 and metallic. 



Oxygen has no effect on it. The simple combus- 

 tibles decompose it when assisted by heat, and some- 

 times take fire, in consequence of its action on them, 

 a proof that this acid is a supporter of combustion. 



The simple incombustibles have no action on it. 

 It oxidizes several of the metals, especially when as- 

 sisted by heat. 



It combines with the salifiable bases, and forms a 

 class of salts called arienialcs. 



Jt has no action on any of the acids already de- 

 scribed. 



From the analysis of Proust, it appears that this Compou- 

 acid is composi-d of tiou.i 



65 arsenic. 

 35 oxygen. 



100 





