80 LEAD, SALTS OF 



From No. 5 to No. 9 the diameter decreases by regular gradations, the latter being 

 only 3 g 5 th of au inch. 



The operation is always carried on with three cullenders at a time, which are sup- 

 ported upon projecting grates of a kind of chafing-dish made of sheet-iron somewhat 

 like a triangle. This chafing-dish should be placed immediately above the fall, while 

 at its bottom there must be a tub half-filled with water for receiving the granulated lead. 

 The cullenders are not in contact, but must be parted by burning charcoal in order to 

 keep the lead constantly at the proper temperature, and to prevent its solidifying in the 

 filter. The temperature of the lead-bath should vary with the size of the shot ; for the 

 largest, it should be such that a bit of straw plunged into it will be scarcely browned, 

 but for all it should be nicely regulated. The height from which the particles should 

 be let fall varies likewise with the size of the shot ; as the congelation is the more 

 rapid, the smaller they are. With a fall of 33 yards or 100 feet, from No. 4 to No. 9 

 may be made : but for larger sizes, 150 feet of height will be required. 



Everything being arranged as above described, the workman puts the filter-stuff 

 into the cullender, pressing it well against the sides. He next pours lead into it with 

 an iron ladle, but not in too great quantity at a time, lest it should run through too 

 fast. The shot thereby formed and found in the tub are not all equal. 



The centre of the cullender being less hot affords larger shot than the sides, which 

 are constantly surrounded with burning charcoal. Occasionally, also, the three cul- 

 lenders employed together may have holes of different sizes, in which case the tub 

 may contain shot of very various magnitudes. These are separated from each other 

 by square sieves of different fineness, 10 inches broad and 16 inches long, their bottoms 

 being of sheet-iron pierced with holes of the same diameters as those of the cullenders. 

 These sieves are suspended by means of two bands above boxes for receiving the 

 shot ; one sieve being usually set above another in consecutive numbers, for instance, 

 1 and 2. The shot being put into the upper sieve, No. will remain in it ; No. 1 will 

 remain in the lower sieve, and No. 2 will, with all the others, pass through it into the 

 chest below. It is obvious that by substituting sieves of successive fineness, shot of 

 any dimensions may be sorted. 



In the preceding process the shot has been sorted to size ; it must next be sorted to 

 form, so as to separate all the spheroids which are not truly round, or are defective in 

 any respect. For this purpose a board is made use of about 27 inches long and 16 

 broad, furnished partially with upright ledges ; upon this tray a handful or two of the 

 shot to be sorted being laid, it is inclined very slightly, and gently shaken in the hori- 

 zontal direction, when the globular particles run down by one edge, into a chest set to 

 receive them, while those of irregular forms remain on the sides of the tray, and are 

 reserved to be re-melted. 



After being sorted in this way, the shot requires still to be smoothed and polished 

 bright. This object is effected by putting it into a small octagonal cask, through a 

 door in its side, turning upon a horizontal iron axis, with rests in plummer boxes at its 

 ends, and is made to revolve by any mechanical power. A certain quantity of plumbago 

 or black-lead is put into the cask along with the shot. 



X.EAD, SALTS OP. The following are the chief artificial salts: 



CARBONATE OF LEAD. See WHITE LEAD. 



NITKATE OF LEAD (Nitrate de plomb, Fr. ; Salpeters'dures bleioxyd, Ger.), is made 

 by saturating somewhat dilute nitric acid with oxide of lead (litharge), evapo- 

 rating the neutral solution till a pellicle appears, and then exposing it in a hot 

 chamber till it be converted into crystals, which are sometimes transparent, but gene- 

 rally opaque white octahedrons. Their spec. grav. is 4'068 ; they have a cooling, 

 sweetish, pungent taste. They dissolve in 7 parts of cold, and in much less boiling 

 water ; they fuse at a moderate elevation of temperature, emit oxygen gas, and pass 

 into oxide of lead. Their constituents are 67'3 oxide and 327 acid. Nitrate of lead 

 is much employed in the chrome-yellow style of CALICO-PRINTING. 



There are three other compounds of nitric acid and lead oxide : viz. the bi-basic, 

 the tri-basic, and the sex-basic ; which contain respectively 2,3, and 6 atoms of base to 

 1 of acid. 



OXYCHIOBIDB OF LEAD. A white pigment patented by the late Mr. Hugh Lee 

 Pattinson, of Newcastle, which he prepared by precipitating a solution of chloride of 

 lead in hot water with pure lime-water, in equal measures ; the mixture being made 

 with agitation. As the operation of mixing the lime-water and the solution of 

 chloride of lead requires to be performed in an instantaneous manner, the patentee 

 prefers to employ for this purpose two tumbling boxes of about 16 feet cubic capacity, 

 which are charged with the two liquids, and simultaneously upset into a cistern in 

 which oxychloride of lead is instantaneously formed, and from which the mixture flows 

 into other cisterns, where the oxychloride subsides. This white pigment consists of 

 one atom of chloride of lead and one atom of oxide of lead, with or without an atom 

 of water. 



