IRON. 



of lead is precipitated, and an oxy-acetat is held in folution 

 of a beautiful reddilh-brown colour. This fait does not 

 afford cryfta's. It has the fmell of vinegar ; and, when in 

 folution, affords an excellent teft for arfenic. The arfenic 

 forms an info'.uble compound with the iron, of a brilliant 

 orange tint. Tiie pyrolignic acid, which is an impure 

 acetic acid, unites v\nth iron, and yields a very cheap acetat 

 of iron, which is ufed by dyers and calico printers as a 

 mordant. 



Succinat of Iron — When the folutions of fuccinat of pota(h 

 or foda, and fulphat of iron are mixed together, a brownifh- 

 red infoluble precipitate is formed, which is the fjccinat of 

 iron. The foluble fuccinat may hence be employed to 

 feparate iron from other fubftances. 



It is compofed of 



Acid and water 61.5' 

 Oxyd - - 38.5 



The exalat, tartarat, cUrat, malat, iciizoat, and fuhcrat of 

 iron, are but little known. They are all, however, foluble 

 in water. 



Gallat of Iran. — When the gallic acid is added tc any 

 folution of iron, the oxyd being at a minimum of oxydation, 

 a fine purple precipitate will be produced. If the acid 

 be entirely freed from tan, the purple colour is much more 

 confpicuous. The pure gallic acid, therefore, is much 

 better as a teft for iron, than the mere infufion of galls. 



The tan may be feparated from this acid by means of 

 gelatine, which does not precipitate the gallic acid. By 

 this treatment a folution may be obtained colourlefs and 

 limpid. 



If the gallic acid be added to a fait of iron, in which 

 the oxygen is at a maximum, the precipitate is a very com- 

 plete black ; but the oxyd foon feparates, and falls to the 

 bottom in the form of a red powder. This property renders 

 thefe falts of iron unfit for making writing ink. When the 

 oxyd is in the ftate of prot-oxyd, the combination is per- 

 manent ; and although it is not fo black when firft ufed, 

 it foon becomes dark by expofure to the air. We may 

 hence learn, that while ink is in ufe, it (hould not be kept 

 expofed to air ; fince it paffes to the ftate of oxy-gallat, and 

 the oxyd will fall down. 



Prujftat of Iron. — When the triple pruffiat of potafii and 

 iron is poured into a folution of the latter fubttance, the 

 oxyd being at a minimum of oxydation, a white powder is 

 precipitated, which is the pruffiat of iron. If this powder 

 be expofed to the air, it changes to a blue ; and in this ftate 

 IS called the oxy-pruffiat of iron. 



Oxy-prujfiat of Iron. — This fait is formed by the fume 

 foluble pruffiat being added to the oxy-fulphat of iron, and 

 conftitutes the beautiful blue pigment, known by the name 

 of Prujpan blue. It is generally, however, adulterated with 

 alumine. See Prussian Blue and Prussic Acid. 



Arfeniat of Iron. — The native arfeniat has been already de- 

 fcribed in the mineralogical part of this article. Arfeniat of 

 potafli, or ammonia, being added to the fulphat of iron, an 

 infoluble powder precipitates, which is the artificial arfeniat 

 of iron. 



Oxj-arfentat of Iron. — The arfeniat of iron, in common 

 with all the other falts of this metal, combines with an extra 

 dofe of oxygen, conftituting the oxy-arfeniat. The pre- 

 cipitate formed by the arfenic acid and the oxy-acetat of 

 iron is of a blueifh-white colour. 



The oxy-arfeniat of iron, from the analyfis of Chcncvix, 

 is compofed of 



Arfenite of Iron. — The arfenious acid, or the common 

 white arfenic of commerce, forms with iron peculiar com- 

 pounds, which have been but httle examined. It does nol 

 take the oxyd of iron from the fulphat, but decompofes the 

 acetat, forming with the protoxyd a fubftance of a greenith- 

 yellow colour ; the precipitate from the oxy-acetat being of 

 a bright orange. If either of the acetats contain the leaft 

 portion of the fulphat of iron, it prevents the precipitation 

 of the arfenite. 



Chromat of Iron. — See Chroiie. 



Moft of the other acids combine with iron ; but they form 

 compounds which are but little known. Certain alkaline 

 falts aft upon iron, and produce triple compounds, which 

 have not received a particular examination. When the ni- 

 trat of potafh is fufed in contaft with that metal, the acid is 

 decompofed, and the iron oxydized to a maximum. This 

 melted mafs, after the acid is completely difGpated, is of 

 a red colour. If, before it becomes deliquefcent, which 

 takes place from the prefence of the alkali, it be thrown into 

 water, the alkah diffolves a quantity of iron, forming a fo- 

 lution of a deep fplendid purple tint. The colour remains 

 permanent for fome time, if the air be excluded ; but, if ex- 

 pofed in an open veffel, it changes quickly to a green, and 

 the oxyd ultimately precipitates, leaving the liquid cleai- 

 and Golourlefs. The precipitated oxyd is of a deep red 

 colour. 



Defcription of Plates. 



Plate I. fig. I, a plan of an iron forge ; fig. 2, an ele- 

 vation of the fame, ^xi fig. 1. A i"; a water-wheel, which 

 gives motion to the ftamping hammer E ; G, the mill-dam ; 

 H, the tail water courfe ; I is a fmall water-wheel, 

 to give motion to the blowing machinery; 1^, fig. 1, is an- 

 other water-wheel, which works the hammer 0, for drawing 

 the balls, &c. into bars ; K is the mill-dam for fupplying all 

 the wheels. 



Q, in^/fjr. I, is a refinery, technically called ^ fimry ; 

 in fig. 2. is the elevation. It is blown by the double blowing 

 cylinders, e, e. R, the ehafery for heating the m.affes of 

 iron a fecond time after hammering ; S, S, plans of balling 

 furnaces, and fimilar to the puddling furnace. 



Plate II. _^. I. is a front view of the finery, as feen 

 fig. 2. Plate I. ; fg. 2. being a fide view. K, the hearth 

 on which the pig-iron and charcoal is placed ; G H, the 

 chimney ; f, the air-pipe ; g, a cock to regulate the blaft ; 

 /}, a leathern pipe conneftiag the main-pipe with the nofe- 

 pipe ; /, fg. 3, an enlarged view of the tuyere-iron, into 

 which the nofe-pipe i is inferted, and which enters the 

 hearth at a, fig. i.; m and n are two iron pipes, terminating 

 in, and forming a part of the tuyere-iron. The pipe m 

 communicates with a ciilern of water, which conveys a 

 ftream of cold water, for the purpofe of keeping the tuyere- 

 iron cool, and which is difcharged at n, into the ciftern 0, 

 fig. 4, where the whole of this apparatus is feen. The fur- 

 nace called the run-out furnace is very fimilar to the finery. 

 The hearth of the finery is fuiroundcd with caft-mctal plates, 

 having a cavity under the bottom plate, to throw water 

 from time to time to keep the bottom plate cool. The run- 

 out furnace differs from this, in being furrounded on three 

 fides with water. This furnace, and its ufe, has al- 

 ready been defcribed. The ehafery is alfo fimilar to the 



finer)', 



