Boiler Incrustations. In a lengthy article on the subject, which appeared in the " Scientific American," Professor Chandler gives the substances referred to in the four following receipts, as having been recommended by practical men, for the purpose of preventing incrustations in boilers:

2330. Wood Chips, Bark, etc.

2330. Wood Chips, Bark, etc.., as a Preventive of Incrustation. Catechu, nut-galls, oak bark, shavings and sawdust, tan bark, tormentilla root, mahogany, logwood, etc. These substances all contain more or less tannic acid, associated with soluble extractive and coloring matters. "When they are introduced into the boiler, the soluble constituents are dissolved by the water, and basic tannate of lime is formed, which separates as a loose deposit, and does not adhere to the sides of the boiler. It is preferable to use the aqueous extract, as sawdust, chips, etc., are liable to find their way into the cocks and tubes, although they act mechanically, receiving incrustations which would otherwise fasten themselves on the sides of the boiler. In selecting one of these substances, the principal object is to secure the largest quantity of tannic acid and soluble extractive matter for the lowest price. Some of these substances are said to be very effective, 1/2 pound of catechu being sufficient for 100 cubic feet of water. From 4 to 6 pounds of oak chips have been recommended per horse power, or 1/2 bushel mahogany chips for every 10 horse power.

2331. Mucilaginous Substances as Preventives

2331.     Mucilaginous Substances as Preventives. Potatoes, starch, bran, linseed meal, gum, dextrine, Irish moss, slippery elm, marshmallow root, glue, etc. These substances form, sooner or later, a slimy liquid in the boiler, which prevents more or less completely the settling and hardening of the deposits. Some of them may even hold the lime and magnesia in solution. Potatoes have been used for many years, wherever steam engines are employed; half a peck or a peck are thrown into the boiler weekly. Linseed meal mixed with chopped straw was employed on a German railway, a peck at a time being introduced into each boiler. Some writers object to these organic substances, on the ground that they are liable to cause frothing.

2332. Saccharine Matter as Preventives

2332.    Saccharine Matter as Preventives. Sugar, molasses, corn or potato syrup. Both cane and grape sugar form soluble compounds with lime salts, and consequently prevent their separation as incrustations. One engineer found that 10 pounds of brown sugar protected his boiler for two months; another, that 6 pounds of corn starch syrup had a similar effect. Another used molasses with success, introducing a gallon at a time.

2333. Fatty Substances as Preventives

2333.     Fatty Substances as Preventives. One writer used whale oil to prevent incrustations, 2 or 3 gallons at a time. Others smear the inside of the boiler with various mixtures of a fatty character. Stearine, mixed with wood ashes, charcoal and tar, has been recommended, or tallow, with soap and charcoal diluted with oil or tar, or tallow and graphite. This plan could not well be applied to a locomotive boiler with its numerous tubes, even though it should prove effective in cylinder boilers.