344 DESTRUCTIVE EFFECT OF IRON-RUST. 



Similar cases, where oxide of iron acts destructively upon organic 

 substances, frequently occur in everyday life. If, for example, linen 

 or cotton cloth in which there are inkstains is repeatedly washed with 

 lye, the texture of the stained spots becomes tender, or even falls out. 

 Like injury is done by the lustre (? J colors, (rust-yellow and black- 

 brown,) Avhich are fastened upon the cloth by first soaking it in a 

 solution of sulphate of protoxide of iron or protoxide of manganese, 

 passing it when dry through lye of caustic potash, and then exposing 

 it to the air, by which the protoxide is changed into oxide. By this 

 process the cloth loses its durability, and the commoji saying is, that 

 it is burnt in dyeing. But this diminution of the strength of the cloth 

 is not an exception, produced by a mistake in the application of the 

 method; it is the normal result. As an explanation of this process, 

 it was supposed that any oxydizing substance may dispose any other 

 with which it is in contact to combine with oxygen, even when other- 

 wise not inclined to such combination. According to Kuhlmann, 

 however, the oxide of iron directly transfers the oxygen to the cloth, 

 and ceases its action only when the destruction is complete. 



Several phenomena, observed in bleaching, can be explained in the 

 same manner. If, for instance, the inner surface of the soaking tubs 

 made of sheet-iron and used in dyeing or bleaching becomes bare 

 by the removal of the calcareous sediment, and if the cloth comes 

 into immediate contact with the iron, then those places to which the 

 air has access are covered with rust, and the strength of the cloth is 

 inevitably impaired. In bleaching the ordinary goods, which are 

 made from refuse cotton, all the parts of the material which in the 

 carding process have become soiled with iron are exposed to this 

 oxydizing action, and this often to such a degree that V\nthin four or 

 five days holes are eaten through the texture. 



Kuhlmann thinks that this energetic action of the oxide of iron is 

 an additional condition for the spontaneous combustion of refuse cot- 

 ton and wool, which so often occurs. It is true the ready reception 

 of oxygen by the oil, with which such refuse is always more or less 

 saturated, favors the spontaneous ignition, yet the oxide of iron may 

 frequently afford an additional cause and favor the commencement of 

 the combustion. 



The objection to the use of iron nails, which we mentioned, is of 

 suflicient importance to induce us to look for a remedy. In order to 

 avoid the destructive action of rust upon wood-work, copper nails 

 must be used instead of iron ones, wherever the first cost is not an 

 essential object. They are, however, too expensive for general use, 

 and therefore iron nails coated with tin or zinc should be substituted. 



How important inferences for agriculture may be drawn from these 

 observations, we shall see in another article. 



