CO129-614-1 Commission of Inquiry into fire at West Point- report 26-5-1949 - 22-12-1949 — Page 89

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(e) Theory of ignition by the agency of impure caustic soda.

Ordinary caustic soda is a corrosive but uninflammable chemical substance, but there exist commercial varieties which are extremely can- gerous, and which have been noted in the Colony this year.

Such caustic soda contains a proportion of the metal sodium, and bursts into flame on being wetted with a few drops of water. The flame is roughly proportional to the amount of water touching the soda, This caustic soda is externally similar to the pure material in common use, being packed in the same type of drums, which are normally corroded and rather battered. In appearance it is light gray to dark gray or even black, whereas the pure solid is white.

Of all the caustic soda in godown No.. 5, only eight drums of this inflammable sod.. were found. These are all in stack No. 29, and their position is el ewn in the enlarged plan of this stack (Plan No. 2). All these cight drums when examined were intact, and showed no signs of the foaming, spattering or bursting, that would have occurred had water accidentally dropped on to their contents.

It will be noted that two empty drums were found on this stack, as shown in Plan No. 2. At one time it was thought that some of the soda was in the process of being repacked into one or other of those drums. It might thus have stood open all night, and become inflamed through e. water drip from the courtyard above, thus setting alight to the lacquer stack No. 40 adjacent. This theory was disproved by the absence of any trace of caustic soda on either of the Crums.

In spite of the presence of this barporous material, therefore, it appears unlikely that the fire originated therein.

6.

Finel theory of origin; properties ol' altrato film.

This brings us to the last theory formed; that of the oause of the fire being self-ignition, or spontaneous combustion, of the washed film.

Theories of spontaneous combustion ere always to be formulated and treated with considerable reserve, ns the process is a comparatively rare one. However, celluloid is one of the materials in which this pho- nomenon has been frequently observed, and studied to a considerable ex- tent.

In the present case, due to a lucky combination of circun- stances, it has been possible to develop the hypothesis of self-ignition and to account for the origin of the fire with reasonable certainty.

(2)

Composition of nitrate motion picture film and washed film.

Nitrate motion picture film is made from a variety of celluloid; that is, a mixture of nitrocellulose and camphor, roughly in the propor- tions of 5 to 1. To this are added small quantities of plasticizing and stabilizing agents, some of these being in the nature of "trade secrets".

Upon this is coated the "emulsion", the sensitized gelatine surface which records the imago; and often, in addition, other coatings are laid upon commercial film, in order to prolung its life, reduce its fire hazard, or for other reasons.

Every year the great motion picture companies accumulate very large quantities of old film, in the form of studio waste and of unser- viceable film returned from their cinema circuits. This material is recovered by a process of washing, which removes the gelatin emulsion and leaves the original celluloid base. This material is known as "washed fil".