PADDING MACHINE 



469 



ozone. Faraday found that a mixture of iodide of potassium and starch was decom- 

 posed at the positive pole, even after the gaseous oxygen had been made to pass 

 through a tube containing a layer of cotton soaked in a solution of potash. The 

 object of this arrangement was to arrest any acid which might be simultaneously 

 produced, and thus lead to the decomposition of the iodide. Dr. Letheby found that 

 the ozone thus evolved at the positive pole possessed the same power of colouring 

 strychnia as the oxygen (ozone) liberated by sulphuric acid from the peroxides of 

 manganese and lead, and from chromic acid. 



In 1850, Schonbein found that ozone was a product of the slow combustion of etJicr. 

 If a small quantity of ether be poured into a jar or bottle, and a clean glass rod, 

 heated to about 500, is introduced, acid vapours are given off which redden wetted 

 litmus at the mouth of the jar, and which set free iodine from iodide of potassium, 

 causing the blueing of starch-paper impregnated with this salt. Clean platinum, and 

 even copper or iron, will produce similar effects. The residuary ether in the jar at 

 the same time acquires new properties those of antozone. It bleaches sulphate of 

 indigo, and converts chromic into perchromic acid. Antozone is usually produced 

 during this slow combustion of ether, but its existence as a separate principle is ex- 

 ceedingly hypothetical it is probably a peroxide of hydrogen. See ' Ozone and 

 Autozone,' by Cornelius B. Fox, M.D. ; and "Watts's 'Dictionary of Chemistry.' 



PACK.FONG. An East Indian alloy, forming a white metal like German silver. 

 It is the Chinese nickel-silver. It appears to contain copper, zinc, and nickel. 



PACO, or PACOS, is the Peruvian name of an earthy-looking ore, which con- 

 sists of brown oxide of iron, with almost imperceptible particles of native silver dis- 

 seminated through it. 



PADDING MACHINE (Machine a plaquer, Fr. ; Klatsch, or Grundermaschine, 

 Ger.), in calico-printing, is the apparatus for imbuing a piece of cotton cloth 

 uniformly with any mordant. In fig. 1582, A BCD represents in section a cast-iron 

 frame, supporting two opposite 

 standards above M, in whose ver- 

 tical slot the gudgeons a b of two 

 copper or bronze cylinders, K F, 

 ruu ; the gudgeons of E turn upon 

 fixed brasses or plummer blocks ; 

 but the superior cylinder F rests 

 upon the surface of the under one, 

 and may 



it with greater or less force by 

 means of the weighted lever d efg, 

 whose centre of motion is at d, 

 and which bears down upon the a 

 axle of F. K is the roller upon 

 which the pieces of cotton cloth 

 intended to be padded are wound, 

 several of them being stitched 

 endwise together. They receive 

 tension from the action of a 

 weighted belt, on, which passes 

 round a pulley, n, upon the end of 

 the roller K. The trough G, which 

 contains the colouring-matter or 

 mordant, rests beneath the cylinder c[ 

 upon the table L, or other conve- 

 nient support. About two inches above the bottom of the trough there is a copper dip 

 roller, c, under which the cloth passes, after going round the guide roller m. Upon 

 escaping from the trough, it is drawn over the half-round stretcher-bar at i, grooved 

 obliquely right and left, as shown at N, whereby it acquires a diverging extension 

 from the middle, and enters with a smooth surface between the two cylinders E F. 

 These are lapped round 6 or 7 times with cotton cloth, to soften and equalise their 

 pressure. _ The piece of goods glides obliquely upwards, in contact with one-third 

 of the cylinder F, and is finally wound about the uppermost roller H. The gudgeon 



