t o guncotton, sucrose acetate, a substitute for cellulose acetate, and sucrose benzoate.
PAINTS FOR INDICATING THE USES OF PIPES Engineering, 95, 607, states that in xgrx German engineers a n d metallurgists came to a preliminary understanding that it was desirable to mark pipes carrying certain fluids by certain colors, so as to avoid confusion. The question has since been discussed by technical institutions and chemical manufacturers. I t was natural that conflicting wishes should be expressed, for in each works some particular kinds of pipes may predominate o r coexist, and the managers naturally desire to make certain distinctions particularly easy. The majority of authorities have, however, now agreed that the following colors should be used for the following purposes: Water, green; gas, yellow; air, blue; steam, white; acid, pink; lyes, violet; oils, brown; tar, black; and vacuum, gray. I t is recommended that pipe conduits for high tension electric currents be marked red, like acids, as red would be the danger color; the forked-lightning arrow might be added as a distinctive mark. I t is proposed that a n ordinary steam-pipe should be white; a red ring mould indicate a pressure of more than z atmospheres; z red rings, high-pressure superheated steam: and a green ring mould distinguish the exhaust-pipe. A dark red ring on a pink or violet acid or lye pipe would intimate that the acid or lye carried was concentrated. A black ring would stand for carbon or a n impurity; a tar-oil would be brown with a black ring; a refusewater pipe green with a black ring. Pipes for ordinary gas or for purified blast-furnace gas would be painted yellow: the red ring might indicate coke-oven gas, the black ring blast-furnace gas not purified, the green ring water-gas, the blue ring producergas, etc. I n blue air-pipes the red ring would indicate high pressure, a white ring hot air. Potable water pipes might be green with white dots; pipes carrying slimes, green with black dots. Letters might be employed to distinguish different gases and liquids. Small iron labels or rings a few inches in width, properly colored and then varnished or enameled, would cause much less expense. I t is the opinion of German engineers that enameled rings, directly clamped around the pipes, are most convenient. A SELF-EQUALIZING EXPANSION JOINT The “Badger” self-equalizing expansion joint is a corrugated copper joint having external rings and is designed to take u p changes in length of pipe lines conveying steam, water or air. The external rings on the corrugations distribute the strain and by thus bringing many corrugations into service no one of them is called upon to take more than its share of the strain. The rings force a part of the strain to the next corrugation, a n d , as each corrugation has only a slight movement, Ihe joint is said to last almost indefinitely. The number of corrugations depends upon the pressure and upon the length of the joint. For high pressures and superheated steam the change in length is considerable, and, therefore, more corrugations are used; for very low pressures, as in exhaust piping, z or 3 are sufficient for the slight alteration in length. I n some cases where the expansion is small but the vibration must be taken up, the joint does not require any external rings; these, however, add strength and also stiffen the exhaust pipe against collapse. This new joint is said to require no packing and to take up no more room than a pipe fitting. A NEW TYPE OF PULVERIZER A German firm has placed on the market a pulverizing machine with conical cylinders, and constructed in such a manner that it is dust-proof and perfectly automatic. .It is designed to grind substances to a fine state of subdivision and to simultaneously
produce intimate mixtures. The construction is shown in the accompanying figures. This pulverizer is claimed to be more efficient than any other type i u ~:he following substances : chemical products, mineral colors, dyes, feldspar, barite, ores, chalk, gypsum, clay, white lead, lithopone, ultramarine, resins, saltpeter, salt, lime, coal,
cement, sand, coke, cork, flour, manure, graphite, chamotte, etc. I t is claimed that the machine is particularly useful for mixing aniline dyes with vegetable dyes. The material is charged into the conical drum by way of a fixed hopper. At the base of the drum is a scoop which returns the material to the drum a t every revolution, thus effecting intimate grinding and mixing. -4 man-hole is provided on the side for cleaning the interior of the drum.
