Page:Pyrotechnics the history and art of firework making (1922).djvu/151

 After that date, however, it is not too much to say that quite as large a proportion of accidents were due to the admixture of chlorate of potash and sulphur.

We are, of course, now speaking of accidents during manufacture, although to the same cause may be attributed many of the numerous cases of bursting mortars during displays which were so frequent until the prohibition of this mixture in 1894 by Order in Council 15.

Dr. Browne, of Hull, a consulting chemist, published in 1884 a book entitled, "Firework Accidents, their cause and prevention," in which he divides accidents into three classes: mechanical, chemical (spontaneous combustion), and mechano-chemical.

Such a classification seems to the writer misleading, as all accidents must of necessity be chemical; that is to say, for combustion chemical action must take place; and with the exception of cases where ignition has taken place quite spontaneously, that is where the composition has ignited when lying perfectly undisturbed, all must be considered mechanical.

Almost any composition used in pyrotechny, however stable, can be ignited by a violent blow between two hard surfaces, but some compositions are so unstable as to be ignited by very slight friction.

It is therefore a question of degree, or whether the mechanical factor is most to blame or the chemical. A better classification would be:

I. Ignition caused by violence, friction or heat.

II. Accidents caused by the state, condition or quality of the composition or ingredients.

If the accident be included in the class which gives the fundamental cause of the accident, it will be found that the