BLUE VITRIOL 407 



described : * A common wide-mouthed bottle is carefully fitted with a caoutchouc cork 

 bored -\vith two holes, into each of which passes a piece of glass tube bent at a right 

 angle. On to one of these tubes is slipped the caoutchouc tube coming from an 

 ordinary caoutchouc bellows, whilst the other is put in communication with the 

 blowpipe nozzle by means of four pieces of caoutchouc tubing joined by three pieces 

 of glass tube, drawn to a fine point at each end. This forms the main peculiarity of 

 the arrangement. When air is forced into the bottle by the blower in jerks, it finds 

 a difficulty in escaping as fast as it comes in, on account of the six fine openings in 

 the glass tubes that it has to pass through on its way from the bottle to the nozzle, 

 and it thus acquires a certain pressure in the bottle, and flows out towards the nozzle 

 as a regular blast. The bottle may be about 6 inches high by 3^ inches wide, with a 

 neck 1 inch in diameter; but the dimensions are of no great importance. On the 

 whole a somewhat large bottle is better than a small one. The pieces of glass tube 

 we employ are 2 inches long by |rd inch in diameter. The apparatus will be stronger 

 if instead of a glass bottle a tin cylinder is used, about 4 inches high by 2 inches in 

 diameter, with two tin tubes opening into its top. Small metal cylinders with a fine 

 hole at each end may be used instead of the little glass tubes.' 



Many blowpipes have been invented for the employment of oxygen and hydrogen, 

 by the combustion of which the most intense heat which we can produce is obtained. 

 Professor Hare, of Philadelphia, was the first to employ this kind of blowpipe, when 

 he was speedily followed by Clark, Gurney, Leeson, and others. The blowpipe, fed 

 with hydrogen, is employed in many soldering processes with much advantage. 



The general form of the ' workshop blowpipe ' is that of a tube open at one end, 

 and supported on trunnions in a wooden pedestal, so that it may be pointed vertically, 

 horizontally, or at any angle as desired. Common street gas is supplied through 

 one hollow trunnion, and it escapes through an annular opening, while common air is 

 admitted through the other trunnion, which is also hollow, and is discharged in the 

 centre of the hydrogen through a central conical tube ; the magnitude and intensity 

 of the flame being determined by the relative quantities of gas and air, and by the 

 greater or less protrusion of the inner cone, by which the annular space for the hy- 

 drogen is contracted in any required degree. See AUTOGENOUS SOLDERING. 



BLUBBER. The cellular membrane of the whale, containing the oil. See 

 OIL. 



BLUE COPPERAS, or BLUE STONE. The commercial or common names 

 of sulphate of copper. See COPPEE, SULPHATE OF. 



BLUE GUM. The Eucalytus globulus (Lab.), a tree common in Tasmania and 

 South-Eastern Australia, and valuable for its timber and for the gum which it 

 secretes. 



BLUE IRON-ORE. See VIVIANITE. 



BXiUE JOHN. A beautiful variety of fluor spar, found at Tray Cliff, near Castle- 

 ton, Derbyshire, from which vases and other ornamental articles are wrought. It is 

 now becoming scarce. See FLUOR SPAB. 



BLUE IiEAD. A name used sometimes by the miners to distinguish galena from 

 the carbonate, or white lead. A variety of galena, to which this name has been applied, 

 and which is pseudomorphous after pyromorphite, has been found at Herodsfoot 

 mine, and Huel Hope in Cornwall, and at some mines in Saxony and France. The 

 specimens from Huel Hope would burn in the flame of a candle like the supersulphide 

 of lead. 



BXiUE PIGMENTS. The blues of vegetable origin, in common use, are indigo 

 and litmus. The blue pigments of a metallic nature found in commerce are the fol- 

 lowing : Prussian blue ; sesqui-ferrocyanide of iron, called also Berlin blue ; moun- 

 tain blue, a carbonate of copper mixed with more or less earthy matter ; Bremen blue, 

 or verditer, a greenish-blue colour obtained from copper mixed with chalk or lime ; 

 iron blue, phosphate of iron, but little employed ; cobalt blue, a colour obtained by cal- 

 cining a salt of cobalt with alumina or oxide of tin ; smalt, a glass coloured with 

 cobalt and ground. 



Molybdenum blue is a combination of this metal and oxide of tin, or phosphate of 

 lime. A blue may also be obtained by putting into molybdic acid (made by digesting 

 sulphuret of molybdenum with nitric acid), some filings of tin, and a little muriatic 

 acid. The tin deoxidises the molybdic acid to a certain degree, and converts it into 

 the molybdous, which, when evaporated and heated with alumina recently precipitated, 

 forms this blue pigment. 



Ultramarine is a beautiful blue pigment. 



TurnbulFs and Chinese blues are both double cyanides of iron. 



King's blue. A carbonate of cobalt. 



Saxon blue. A solution of indigo in sulphuric acid. 



BXiUE VXTRXOIi. Sulphate of copper. When found in nature, it is duo entirely 



