ELECTRICAL PRODUCTS BLEACHING-POWDER.

Another industry that has assumed large proportions at Niagara Falls, owing to the vast quantity of electricity produced there, is the manufacture of a commercial product called bleaching-powder, or chloride of lime. Every one knows that chloride of sodium is simply common salt, so extensively used wherever people and animals exist. Simple and harmless as it is, while it exists as a compound of the original elements, when separated into those elements they are each very unpleasant and even dangerous substances to handle. Salt is one of the most common substances in nature. It is found in many parts of the world in solid beds, and is one of the prominent constituents of sea-water.

Salt is a compound of chlorine and a metal called sodium. Sodium in its pure state has a strong affinity for oxygen, so much so that when a lump of it is thrown into water it takes fire and burns violently with a yellow flame. Chlorine, the substance with which it unites to form common salt, is a greenish-colored gas, the fumes of which are very offensive and very dangerous even to breathe, if the quantity is very considerable.

It is a curious fact in nature that two such substances as chlorine and sodium, both of them so difficult and dangerous to handle, should unite together to form such a useful and harmless compound as common salt. The important element in bleaching-powder is the chlorine which it contains. It is extensively used in the manufacture of paper and in all other materials where bleaching is required. The object of combining it with lime, forming a chloride of lime, is simply to have a convenient method of holding the chlorine in a safe and convenient manner until it is needed for use.

The chemical works at Niagara Falls manufacture bleaching-powder on a very large scale. The part that electricity plays is to separate the chlorine from the sodium as it exists in common salt. At the works I was first taken into a room where a large quantity of salt was stored. A belt with little carrier-buckets on it picked up this salt and carried it into another room, where it was thrown into a vast mixing-vat containing water. The salt was mixed with water until a saturated solution was obtained. In a large room, covering one-half acre or more of ground, were assembled a great number of shallow vessels, about 4 by 5 feet square and 1 foot deep. These vessels were sealed up so that they were gas-tight. Communicating with all of these vessels were pipes connecting with the great tank containing the saturated solution of salt.

From the top or cover of each vessel is a pipe running to a main pipe that carries off the chlorine gas into another room as fast as it is formed. Through each one of these vessels a current of electricity passes; the whole system consuming about 2000 horse-power. The electric current, as it passes through the brine, separates the chlorine from the sodium, the chlorine passing in the form of gas up through the pipes, before mentioned, into the main pipe, where it is carried into another large room and discharged into a system of gas-tight chambers. Upon the floor of these chambers is spread a coating of unslacked lime ground into a fine powder. The lime has a strong affinity for the chlorine gas and rapidly absorbs it, forming chloride of lime. When the lime is fully saturated with the chlorine the gas is turned off from that chamber, which is then opened up and the chloride taken out for shipment. A new coating of lime is now spread in the chamber and the gas is turned on and the process repeated.

There are a number of these chambers, so that the operation in all of its phases is going on continuously. The room where the chlorine gas is formed is thoroughly ventilated, a precaution which is very necessary in case any one of the vats should spring a leak, as they sometimes do.

In each one of these vats where the electrolytic process is going on there are two products constantly passing off; one, as before mentioned, is chlorine gas, and the other caustic soda in solution. The solution in the vat is constantly being renewed by the saturated solution of salt from the reservoir before mentioned. There is one stream continuously coming into the vat and two going out, caused by the decomposing power of the electric current. The solution of caustic soda is carried to large evaporating-pans, where the water is driven out of it, leaving the caustic soda in dry, white sticks of crystalline formation. In this process the electric current, which comes from the power-house with an energy of 2000 horse-power, has to be transformed twice; first, to bring it to the proper voltage for the work of decomposition, and, secondly, to change it from an alternating to a direct current, by which all electrolytic processes are carried on.

You will notice that the electrical energy expended in this establishment is double that used in the manufacture of carborundum.

The caustic soda, which is one of the products from the decomposition of salt, is taken to another establishment, where, by still another electrical process, metallic sodium is manufactured. The process here being a secret one, the writer did not have the privilege of examining the details.