Cold ignition

Cold Ignition of Combustionlike Waves of Cryopolymerization and Other Reactions in Solids... 

We emphasize that only brittle disruption was capable to ignite the reaction. A fast interaction of the needle with the san )le, involving time scales of order 0.01-0.1 s is necessary to induce the effect. This is reminiscent of what happens in shock waves. If the m hanical loading of the needle is much slower (times scale of the order of 1 ms), the reaction is not ignited. It means that a plastic deformation is not capable to excite the reactions, and, as suggested by theory, only elastic deformations and following brittle disruption is a necessary condition for cold ignition of cryochemical reactions in solids. 

The results above, used to describe chemical reactions at very low temperature, allowed us to propose an unexpected application of the "cold ignition phemomenon in a very different field of chemistry, namely for high temperature processes of combustion and explosion. 

The silver salts of most carboxylic acids are only sparingly soluble in cold water, and hence are readily prepared. Moreover they very rarely contain water of crystallisation, and therefore when dried can be analysed without further treatment. The analysis itself is simple, rapid and accurate, because gentle ignition of a weighed quantity of the silver salt in a crucible drives off the organic matter, leaving a residue of pure metallic silver. 

When an amine, or a solution of its hydrochloride, is added to an aqueous solution of chloroplatinic acid, a salt of the base with the cliloroplatinic acid, of general formula BjiHiPtCle (where B is one molecule of the base) is formed and usually crystallises out, for these chloroplatinates hai e normally a rather low solubility in cold water. The chloroplatinate can be filtered off, dried, and then analysed by direct ignition, when only the metallic platinum ultimately remains. Knowing the percentage of platinum in the chloroplatinate, the molecular weight of the latter, and hence of the constituent base, can readily be calculated. 

Colourless liquids which ignite in air and decompose explosively in cold water... 

As the cold vapor flowed up the stack, it met condensate flowing down. The condensate froze and completely blocked the 8-in.-diameter stack. The tank was overpressured and ruptured. Fortunately, the rupture was a small one and the escaping ethylene did not ignite. It was dispersed with steam while the tank was emptied. 

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