D. CHEMISTRY AND METALLURGY. 201 



EXPLOSION AND IGNITION BY PERM ANGxYNATE OF POTASH 



AND SULPHURIC ACID. 



According to a series of experiments by Bottger, a mixture 

 of two parts of perfectly dry permanganate of potash with 

 about two to three parts, by weight, of concentrated sul- 

 phuric acid, will frequently cause most violent explosions 

 with, and subsequent ignition of, many substances, especially 

 volatile oils, on contact with them at ordinary temperatures ; 

 as by placing ten to twelve drops of such an oil in a capsule, 

 and stirring into it as much of the mixture as will adhere to 

 the end of a heavy glass rod. Such explosions occur with 

 oil of thyme, of mace, of cinnamon, of rue, of cubeb, of lemon, 

 of marjoram, and of spike, and with rectified oil of turpentine. 

 Simple ignition, without explosion, occurs with oil of rose- 

 mary, of lavender, of cloves, of rose, of geranium, of gaulthe- 

 ria, of caraway, of cajeput, and of bitter almonds, and with 

 rectified petroleum, especially if a small quantity of the oil be 

 dropped on bibulous paper, and then brought in contact with 

 the mixture. At times, however, from unknown causes, ex- 

 plosions have also taken place with these, so that great care 

 is necessary in experimenting with them. Alcohol, ether, 

 wood-spirit, benzole, and bisulphide of carbon ignite instant- 

 ly, without explosion. Dry blotting-paper begins to glow, 

 with the evolution of red fumes, and cotton ignites. Gun- 

 cotton and gunpowder are, however, unaffected. Ordinary 

 illuminating gas was also ignited by it. By triturating per- 

 fectly dry permanganate of potash with dry gallic acid, igni- 

 tion, with scintillation, occurred; and by trituration with tan- 

 nin, ignition with flame. 6 (7, March 19, 1873, 117. 



SOLIDIFICATION OF NITROUS OXIDE. 



As long ago as 1845, Faraday, by means of intense cold, 

 succeeded in freezing nitrous oxide to a solid crvstalline mass. 

 But, unlike liquefied carbonic acid, the liquefied nitrous oxide 

 would not freeze by the cold of its own evaporation. Thomas 

 Wills, however, in some late experiments, has managed to ob- 

 tain a sort of nitrous-oxide snow, like that of carbonic acid, 

 by allowing the liquefied gas, mixed with a strong current of 

 air, to flow through a fine jet. In the case of carbonic acid, 

 as is well known, the current of air can be dispensed with. 



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