great variety of intermingling processes, one dependent on the other.

The products of this industry are so vast and numerous and involve so many processes that it would be an impossibility in this Bulletin to point out and describe all operations in which risks occur, it being the intention to show some of the most commonly occurring accidents for which remedies, to prevent their occurrence, may be applied. Many experimenters, some of whom may be classed as amateurs, are constantly engaged in chemical research work for themselves or for others, but their sole object is to manufacture new products or to reduce the cost of those now being manufactured to a minimum.

The attainment of the necessary knowledge to prevent fires, avoid explosions, and eliminate poison risks is only reached through a technical chemical training, practical knowledge only acquired by hard work, and, in some cases, bitter experience. The average workman met with in certain chemical plants, in many cases, knows little or nothing of the nature or effect of the substances which he constantly handles, this ignorance being fostered by some manufacturers for the purpose of protecting their secrets from their competitors, or keeping the men at work in positions which they would refuse to hold if they realized the dangers of their occupations. Many of the materials are referred to only as dope,' ‚” “stuff,” “liquor," or by initials which have no relation to the name or real composition of the material.

Thousands of combinations, resulting in explosive mixtures, can be made with chemicals, among these being the action of sulphuric acid on sugar, nitric acid on turpentine, chlorate of soda with sulphur, chlorate of soda and a cyanide ground together. and sodium peroxide when combined with resins or mineral oils. Certain processes carried on in rooms containing inflammable gases or vapors may readily cause an explosion: the nitrating of cotton, starch, or wood, by persons unfamiliar with the nature of the resultant product is of grave importance as is the storage of certain chemical products, even in small bulk, near steam pipes, in sunlight, or in rooms or closets which are not properly ventilated and may thus permit the combination of vapors with a resultant explosion and fire.

The range of explosibility of certain gases, evolved in various processes of manufacture, when mixed with air is fortunately somewhat limited, being controlled by certain physical conditions as method of ignition, volume of gas, moisture content of air, temperature, or dilution in a vessel or room. For alcohol vapor the percentage mixed with air is from 4 to 13.6 to cause explosion; for benzol vapor 2.7 to 63; for hydrogen gas 9.5 to 66.5; for carbon monoxide 16.6 to 74.8; and for ether 2 to 6. Above and below these percentages no explosion will occur because in the former the gas is present in too small an amount, while in the latter there is not sufficient air present to support combustion of the gaseous mixture.

ARTIFICIAL LIGHTING OF FACTORIES

Many processes are carried on, in this State, in which the plant is in continuous operation day and night, as in the manufacture of bleach (chlorinated lime), manufacture of trinitrotoluol, extraction of coloring matter from logwood chips, sugar refining, distilling and refining of oils, etc. These require artificial means to light the interior of the plant during the hours of darkness, and, while the light intensity need not be as great as in the textile industry and needle trades trades where constant and close use of the eyes is necessary, the necessity of sufficient lamps to eliminate shadows, properly light passageways, tanks, vats, and machines is of great importance, it being necessary to supply at least one-quarter of a foot-candle of light at the floor level and a greater intensity at the machines according to the character of the work being done thereon.

Explosive dusts, which are found in sugar refineries, vapors or fumes in oil refineries, thinning rooms in varnish works, in the process of ether purification, and in the rectification of alcohol, may be ignited, when present in sufficient quantities, by contact with open lights, or contact with the glowing or heated filaments of electric light globes in the event of the accidental breaking of such globes.

In the course of the survey, two factories were found in which fan-tail gas lights were in use in a room adjoining one in which alcohol was being re-distilled to render it absolute. In another

annato, licorice,

factory open gas lights were used where drugs slippery elm, and cantharides -were being ground and large quantities of dust were escaping from the mills. In still another one, ordinary unprotected 40-watt incandescent electric light globes were in use where compound ethers were being made, and, in two instances, these electric light globes were seen to be lowered, through small openings, into closed tanks containing benzol, for observation of the amount of the liquid in them. The cause of one explosion, which severely burned five employees and set the factory on fire, was definitely determined to have been the ignition of benzine vapor which came into contact with the glowing filament of an electric light globe.

In one instance where large quantities of hydrogen gas were disengaged in a room, it was observed that the switch, used for throwing the lights on and off in the cell room, was located in the same room, and it cannot be too emphatically stated that no greater danger of plant destruction, than the existence of such conditions, presents itself. In this particular case, it was the idea of the superintendent that the gas thrown off was of such a specific gravity that it rose rapidly and escaped through the louvres in the monitor roof, but this idea did not take into consideration the effect of wind velocity and temperature of air outside of the louvre; cold air driven against a louvre, when the temperature of the air of the workroom is considerably higher than that of the outside air, is usually cast downward into the workroom where it can easily deflect a rising column of light gas toward such a switch and cause an explosion of great magnitude. Figure 1 shows safe location for such switches, outside of building.

It must also be remembered that gases may be exploded by heat as well as by flame, this fact being of particular importance in cases where it is necessary to use molten metal, or metal heated to redness, in making repairs in rooms where these gases may be present. Frequent tests should be made to determine the presence or absence of such explosive gases as well as other gases (carbon monoxide, carbon disulphide, or hydrogen sulphide) which may require the temporary suspension of all work in that room or building; the State Industrial Commission, with a well-equipped

laboratory, is always ready to assist the manufacturer in making

such tests.

HEATING

During cold weather, the artificial heating of factories in which chemicals are manufactured or used is essential to prevent the freezing of liquids contained in the tanks, pipes, vats, and in all machines which are used in various processes, and to provide comfort for the employees who work within the buildings.

FIG. 1-Safe position of electric switches for throwing on lights; also fuse plugs located on wall of building in yard, when inflammable liquids and gases are used inside of a factory.

While certain processes are accompanied by the generation of sufficient heat to keep the air of the factory at a comfortable temperature, the majority of factories must be heated by means of stoves of various types, by steam pipes or radiators, or by means of the indirect system of heating in which the circulation of warm air combines heating with ventilation of the factory.

In some factores there were found in use salamander stoves, using coal, coke, or charcoal as fuel, without any means being

provided to convey to the outer air the products of combustion from these devices, but in the majority of cases steam is used as the heating medium. As a rule, steam pipes and radiators are placed along the walls near windows, and on or close to the floor, but this is somewhat dangerous owing to the possibility of there coming into contact with these heated pipes volatile and inflammable liquids, dyes, or chemicals in which certain chemical reactions or changes may occur in the presence of heat.

It was not an uncommon occurrence to find rags, wood, and other refuse lodged between steam pipes or radiators and the walls of the buildings, in some cases this dirt and refuse being found baked into a hard mass under the radiators. In these cases, 66 out of sight, out of mind" would prove to be a costly adage if this refuse should contain oils or resins which would cause the mass to char at a much lower temperature than wood or fibre, as such mass may become ignited, by the action of the heat or by spontaneous combustion, and be the starting point of a costly fire.

Leaky valves or joints may also constitute a fire hazard in cases where the leaking fluid is liable to come into contact with acids, bronze powders, lime (calcium oxide), calcium carbide, or various metals; this leakage may also result in considerable property damage through the rotting of wooden floors and beams, and the erosion of metallic structures by the constant contact and action of the escaping water.

The use of screens or metal deflectors is a fairly effective means of keeping stored material from contact with steam pipes or radiators, but the best method is the elevation of the heating devices to a considerable distance above the floor, thus not only eliminating a possible fire hazard, but giving a greater floor area and preventing the accumulation of dirt under any of the devices. As an economic measure which results in the saving of many tons of coal during a season, several factories use a system whereby the exhausted air from workrooms is freed of dust, gases, and fumes, and re-circulated in the same rooms, but such systems must always be viewed with misgiving unless the devices for screening and washing the spent air are frequently inspected to determine and maintain their efficient operation.

No single fixed standard of temperature and humidity can be