IRON. 



agrees with die former, in not being decompofed ; but 

 merely lakes up the oxyd formed by the oxygen of tlie 

 water, tlie hydrogen being given out in the llatc of ga-<. 

 The foKition is of a green colour ; and, on evaporation, it 

 affords cryflals prefenting the fame appearance. Mr. Da-y 

 has given us feveral ufeful fafts relative to this fait. It 

 was emoloyod by him to great advantage in making fome 

 eiidiometrical experiments. He found that a folution of it 

 abforbs a large- quantity of the nitric oxyd gas, which, in 

 thii fituation, is bettei fitted for abforbing oxygen than 

 by mixing the two gafes together. By abforbing this 

 gns it alTumes a brown colour, and acquires an aflringent 

 talle. Wlien the compound is heated, it appears that the 

 gas is decompofed as well as a portion of water ; fince the 

 iron becomes more highly oxydized, and ammonia is formed. 

 Mr. Davy recommends an infallible method of formirg 

 this fait, by adding muriatic acid to fulphuret of iron. The 

 fulphuretted hydrogen prevents the mnriat from becoming 

 «xy-muriat, which has not the property of abforbing the 

 nitric oxyd. Muriat of iron is very fol.'.ble in water and 

 in alcohol. It is decompofed by the alkalis and alkaline 

 earths, and all falts, the bales of which form infoluble com- 

 pounds with muriatic acid ; fuch as lilver and mercury. 



Oxy-murlat of Iron. — The muriat of iron, like the fulphat 

 and ailrat, is co;iverted into the oxy-muriat by the oxyd of 

 iron pafiing from the ilate of prot-oxyd to that of pcr-oxyd. 

 It (lowly undergoes this change by expofure to the air ; 

 and rapidly, by the agency of thofe bodies which afford 

 oxvgen with greater facility, as the nitric and oxy-muriatic 

 acids. The folution is of a deep brown, but does not afford 

 cryftals by evaporation. It has a powerful, aftringent ta!le, 

 and a peculiar odour. When this fait is diftilled it affords 

 oxy-muriatic acid, leaving in the retort the prot-oxyd of 

 iron. 



If the heat be applied rapidly, the fait fublimes ; not in 

 the tlate of oxy-muriat, but of muriat of iron. 



There is alio a triple fait formed by the muriatic acid 

 with iron and ammonia. This may be prepared by adding 

 iron-tilings to muriat of ammonia. It may either be ob- 

 tained in cryftals by evaporation, or it may be fublimed. 

 In the la'ter (late it is known in medicine by the name of 

 F lores Martls. 



Phofphal of Iron. — The phofphoric acid has little aftion 

 upon iron ; but the acid unites with the prot-oxyd, and 

 forms this compound. 



It is prepared by adding a folution of fulphat ef iron to 

 a fluid mIxTure of phofphat of potafh. The fait precipitates 

 in the form of a blue powder, which is infoluble in water, 

 and does not lofe its colour by expofure to the air. 



The fubdance known by the name of native Pruflian 

 blue, is a phofphat of iron ; but, what is remarkable, it has 

 little colour when dug out of the earth, becoming deeper cm 

 expofure to the atmoiphere. A cryftallized fpecimen, lately 

 brought f'-om Brazil, has been analyfed by Vauquelin, and 

 is compofed of 



.Acid 2 1 



Protoxvd 45 

 Water ' 34 



Oxy-phofphat ofIron.—T\\\s fait is formed by taking ad- 

 vantage of fome oxy-falt of iron and phofphat that is 

 fo uble ; as, for inftance, by adding together the oxy-ful- 

 phat, or oxy-muriat of iron, and the phofphat of foda or of 

 potalh, a white powder will be precipitated, which is the 

 oxy-phofphat of iron. 



This fait is infoluble in water, but diffolves in the muriatic 

 or fnlphuric acids ; from which it may be precipitated, un- 

 changed, by pure ammonia. 



Siib-oxy -phofphat of Iron. — The fait above defcribed is not 

 decompoled by the alkalis like the metallic falts in general. 

 The alkali combines with a portion of the acid only, leaving 

 the fait with an cxccfs of baiV, which is the fub-oxy-phofphat 

 of iron. This fub-oxy-phofphat does not dlffolve in water, 

 or fcarcely in acid ; but it has the fingular property of 

 diffolving in aliiumen, or the white of eggs : and if an 

 alkali be prefent, which is the cafe with the albumen in 

 the fcnim of blood, it affumes a reddifli-brown colour, and 

 is fuppofed, therefore, to be the principal colouring matter 

 of the red blood of animals. 



Filial of Iron. — The liquid fluoric acid attacks iron, or 

 rather takes its oxyd, which is formed by the oxygen of the 

 water, while hydrogen gas is evolved. It has no ftriking 

 properties, or any which it may be important to deftribe. 



Borat of Iron. — This fait, being infoluble in water, is 

 obtained by mixing folutions of borat of foda and fulphat 

 of iron together. It appears in the form of a yellowifh 

 powder, and melts into glafs before the blow-pipe. 



If the oxy-fulphat of iron be employed., an oxy-borat will 

 be obtained. 



Carhonat of Iron. — When iron-filings are mixed with the 

 liquid carbonic acid, and fuffered to remain for fome time, 

 the water will acquire a perceptible ta!le of iron. If it be 

 expofed to the air, a precipitation takes place, either from 

 the gas flying off, or from the fait ^ffuming the ftate of 

 fub-carbonat. The precipitate is of a yellow colour. This 

 fait is frequently found in mineral waters, to which it gives 

 a peculiar odour. The water, by Handing a little while, 

 is not fenfible to any of the teils of iron ; but a yellow pre- 

 cipitatt is found at the bottom of the veflel. 



When a folution of neutral carbonat of potafh is added to 

 a folution of fulphat of iron, a large quantity of iron is 

 difTolved by the carbonic acid, -giving to the fluid a ftrong 

 inky talle. 



This fait is alfo found native in the folid form, of which 

 we have already fpoken in the mineralogical part of this 

 article. 



The common rull of iron, formed by expolmg iron to the 

 air, may be proved to be a carbonat of this metal by its ef- 

 fervefcence with acids. It is, no doubt, from the fohibility of 

 this fait, that iron becomes fo perilhablc by expofure to the 



The fub- carbonat of this fpecics, according to B>.-rgmann, 

 is compofed of 



34 acid 

 76 oxvd 



It appears from fome .xpcriments of Eucholz, that the 

 native carbonat, by heating red-hot, becomes magnetic. 



Acetat of Iron. — The acetic acid, when of moderate 

 ftrength, added to iron-filings, caufes the iron to be oxy- 

 dated by the dcconipolition of the water, while the hydro- 

 gen is fet at hberty. The folution has a fweeiilli, though 

 inky tafte, and emits the odour of vinegar. The beil way 

 of forming this fait is by mixing acetat of lead and fulphat 

 of iron together. The fulphat of lead bccotres infoluble, 

 and the acetat of iron remains in the liquid. Mr. Daw ob- 

 tained this fait by tligtiling the fulphuret of iron with acctie 

 acid. It afforded to him cryflals in fmall prions. 



O.xy-acelat of Iron.— U the oxy-fulphat of iron be ufci 



inltead of the fulphat with the acetat of lead, the fulphat 



3 L 2 of 



