237 



BLUBBER. 



BLUE. 



some cases, where steam is the moving power, the piston-rod of a 

 double-acting blowing-cylinder (in which a blast is produced by every 

 stroke, whether upwards or downwards), is connected directly with 

 the vibrating beam of a steam-engine ; in others the motion is trans- 

 mitted through a series of cranks, so that two, three, or four blowing- 

 cylinders may be worked in succession. These generally force the air 

 into an air-chest of large dimensions, which is usually formed of iron, 

 but sometimes of masonry, and from which it is conducted to the 

 blast-pipes, which are called tuyeres or ticea-s. Barlow, in his ' Treatise 

 on Machinery and Manufactures,' part of the ' Encyclopsedia Metrc- 

 politana,' described a very powerful blowing-machine at Woolwich 

 Dockyard, in which four cylinders supplied air, at a pressure of a 

 quarter of a pound to the square inch, to a large air-chest from which 

 pipes extended to all the forges and fires in the smithy, the pipes being 

 supplied with cocks by which the blast could be turned off or on at 

 pleasure. To ensure equability of pressure, a regulating cylinder, 

 with a piston loaded to the required pressure, was used ; and whenever 

 the pressure exceeded the required amount, it raised the piston, and the 

 air escaped like steam from a safety-valve. Owing to the using of 

 sliding instead of clack or flap-valvea in the blowing-cylinders, this 

 machine worked very quietly. Another mode of regulating the blast is 

 to throw the air from the cylinders into a large iron box inverted in a 

 cistern of water, and somewhat resembling a gasometer, but so fixed 

 as to be incapable of motion. The effect therefore of the condensation 

 of air in the box is to force some of the water out ; and the difference 

 between the level of the water within and without the box forms a 

 measure of the degree of condensation or pressure. In using such an 

 apparatus care must be taken to conduct the air-pipes at so high a 

 level as to render the forcing of water into the furnace impossible. 

 The blast thus produced is exceedingly cold, which is a great disadvan- 

 tage in a smelting-furnace. For a notice of the advantages of a hot 

 blast see IRON MANM-FACTURK. 



The Katcr-teUmtn U a simple kind of blowing-machine the invention 

 of which we have seen attributed to Hornblower, one of the early 

 English improvers of the steam-engine. It consists of two iron boxes, 

 or hollow vessels with their under sides open, suspended from the 

 opposite ends of a vibrating beam, resembling that of a steam-engine. 

 The lower edges of these vessels dip into two cisterns of water, within 

 which, rising above the surface of the water, are pipes connected with 

 the blast or air chamber. When, by the motion of the beam, one of 

 the vessels is forced down into the cistern, it compresses the air 

 enclosed between it and the surface of the writer, and consequently 

 forces it along the blast-pipe. The other vessel, meanwhile, as it rises 

 admits a fresh supply of air through a valve which opens inwards ; and 

 this air is forced into the blast-pipe in like way when the action of the 

 beam is reversed. Another machine of similar character, but still 

 more simple, consists of a cask or cask-like vessel suspended on an axle 

 in a horizontal position, so as to be capable of an oscillating motion. 

 This cask is divided longitudinally by a vertical partition, reaching 

 from the top very nearly to the bottom, and is about half filled with 

 water. When the cask is turned a little upon its axis, as the water 

 retains its level, the air at one side of the partition is condensed, and 

 escapes through a valve into a pipe which conducts to the air-chamber 

 or reservoir; while, owing to the enlargement of the space on the 

 opposite side of the partition, air enters it through a valve opening 

 inwards. On reversing the inclination of the cask, the case is reversed 

 and the air which entered before is expelled, while a fresh supply is 

 drawn in on the opposite side of the partition. This is the most 

 Kirnple form of the apparatus, but far more perfect and more com' 

 plicated machines are constructed on the same principle. 



Barlow, in the ' Treatise ' above cited, described a simple anc 

 powerful blowing-machine used at Sharp and Roberts's engine manu 

 factory, at Manchester, which may be compared to an Archimedean 

 screw, excepting that, instead of raising water, its object is to impe 

 air. It is partly immersed in a reservoir of water, and is turned by a 

 steam-engine. Vaughan's blowing-machine is a well-contrived sub 

 stitute for a cylinder and piston engine, in which the required effect is 

 produced by the backwards and forwards motion of square pistons in 

 two oblong boxes, placed side by side, each of which may be comparec 

 t< i i double-acting cylinder. This contrivance is based upon the rudi 

 bellows used by Chinese smiths. Blowing-machines in which tin 

 current in produced by means of fanners are noticed in BELLOWS ; anc 

 their application to steam-carriage furnaces is alluded to in Sir. AM 

 CA.BHI.M.K. 



BLUBBER. [WIIALK FISHINU.] 

 BLUE, as a pigment. The substances used for this purpose are o 

 very different natures, and derived from various sources : they are al 

 compound bodies, some are natural and others artificial. They are 

 derived almost entirely from the vegetable and mineral kingdoms 

 though the first which we shall describe is partly prepared from anima 

 matter, namely : 



Prutsian Blue. This beautiful pigment was discovered by accident 

 in 1710, by Diesbach, a manufacturer of Berlin; but the method of 

 preparing it was first described by Woodward in the ' Philosophical 

 Transactions ' of 1724. The first step in the operation is to calcine a 

 mixture of potah or ite carbonate, with animal matter that contains 

 nitrogen, as blood, hoofs, or horns, in an iron vessel, till it ceases to 

 burn with flame. The residual matter is then suffered to cool, the 



oluble portion of it dissolved in water, and the solution, when suffi- 

 iently concentrated, yields fine yellow crystals on cooling. Tliis salt, 

 ommonly called ferrocyauide of potassium, or prussiate of potash, is a 

 ouble cyanide of potassium and iron, consisting of 



2 Equivalents cyanide of potassium 

 1 Equivalent cyanide of iron . 



3 Equivalents water . . . 



129-9 

 54-0 



27-0 



210-9 



When a solution of this salt is poured into one of protoaulphate oi ? 

 ron, a perfectly white precipitate is formed, provided no persulphate 

 )e present ; but if the latter salt be present, then the precipitate is of 

 v bluish-gray colour ; in both cases it becomes, by exposure to the air, 

 if a fine blue, and is then washed and dried for use. The chemical change 

 iy which the white precipitate is produced may be thus expressed : 



2(FeCy+2KCy) + 2Fe 



Prussiate of 

 Potash. 



Protosulphato 

 of Iron. 



(FeCy+2KCy)+3FeCy) + 2KOS0 3 . 



v ' 



White Precipitate. 



And on exposure to air, the white precipitate becomes oxidised an4 

 converted into ferrocyanide of potassium, which dissolves, and basic 

 Prussian blue. Neglecting the ferrocyanide of potassium, this change 

 may be thus expressed : 



Cyanide 

 of Iron. 



Basic Prussian 

 Blue. 



The action of strong acids removes the sesquioxide of iron (Fe,0,,)> 

 leaving ordinary Prussian blue (Fe,Cy a = 2Fe, ! Cy. 1 + SFeCy). 



Very commonly the solution of cyanide of potassium and iron, 

 procured from the residue of the calcination, is not put to crystallise, 

 but is added at once to the solution of sulphate of iron. In this case, 

 on account of the excess of potash which it contains, a portion of iron 

 in a state of oxide is precipitated uncombined with the colouring 

 matter ; in order to prevent this from injuring the colour of the 

 pigment, either dilute sulphuric acid is added, which dissolves it 

 without acting on the Prussian blue ; or alum is mixed with the 

 sulphate of iron, and the uncombined potash uniting with its sulphuric 

 acid, alumina is precipitated instead of oxide of iron, which merely 

 dilutes without otherwise injuring the colour of the product. When a 

 solution of a persalt of iron, such as the nitrate, is used, the precipitate 

 is immediately obtained of a fine blue; but this process does not 

 answer in manufacturing. 



Prussian blue is inodorous, tasteless, insoluble in water, alcohol, 

 ether, and oils. It is hygrometric, attracting water strongly from the 

 air, which it retains until heated to nearly 280. Diluted acids do not 

 act upon this substance ; but strong sulphuric acid dissolves it, forming 

 a white compound similar to that of starch and water in appearance. 

 On the addition of water the blue colour is restored. Nitric acid and 

 hydrochloric acid, when concentrated, both decompose it, and the 

 same effect is produced by the alkalies and alkaline earths, but with 

 different results. It is also decomposed by a strong heat. Prussian 



this, on account of the intensity of its colour. Its stability is very 

 considerable, and it is not only used as a pigment but also as a dye. 

 According to Berzelius, it was used in Sweden instead of smalt, to give 

 writing-paper a blue tint, but the paper was found to acquire a dis- 

 agreeable greenish hue. 



Indii/o. This fine blue is extracted from different species of indi</<i- 

 fera in the East Indies and Guatemala in South America. For the 

 methods of procuring the colour from the plant, and the various 

 substances with which it is mixed, we refer to the article INDIUO, here 

 merely stating the properties of the blue pigment usually met with I>y 

 that name in small cubic pieces. The colour is extremely deep, the 

 fracture is earthy, but becomes brilliant and of a copper-red colour 

 when rubbed by a hard body, and according to the degree to which 

 this effect is produced, the better is the incligo reckoned. Even in thi.j 

 state, however, it is mixed with some foreign matters, which inny 

 generally be separated by water, alcohol, solution of potash and dilute 

 acid, hi all of which pure indigo is insoluble. It may also be purified by 

 sublimation, but the process is difficult of management, for if the heat be 

 rather greater than necessary, the indigo is decomposed. Another method 

 of procuring pure indigo is to take the solution of indigo prepared by 

 dyers, and agitate it in contact with atmospheric air. This solution 

 is prepared by mixing blue indigo in powder with lime and a solution 

 of protonilpliatc of iron ; the lime decomposes the sulphate of iron, 

 precipitating its protoxide ; this acting upon the indigo, in the presence 

 of water causes it to combine with hydrogen, by which it is rendered 

 colourless and also soluble in water ; if this solution be agitated with 

 atmospheric air, the indigo, becoming dehydrogenised and regaining its 

 colour, is precipitated, and when washed with a little dilute hydro- 

 chloric acid and dried, it is pure. Indigo, except when used as a 

 water-colour, requires white lead to give it body ; it is a colour of 

 considerable permanency. Strong nitric acid decomposes it, but it 



