WASTE, or BY-PRODUCTS. Waste is that portion of raw material used in :my specific manufacture which is in the proses : rendered useless for that particular line. Wwever, the name is sometimes retained long after a sub stance, at one time of little or no value, has been utilized as raw material in some other industry. In every manufacturing process. me dsameal or chemical. there is more or less left osier material which becomes waste. The ex amples Risen below relate to new waste, hut ready everything we use wears or corrodes. or gets broken or mithapely, and so rags and rust slid straps arise. On the other hand. the rust *kith arises from corroding iron it utter waste, since it can never t* profitably collected at all. There is a kind of waste, for the most part difficult to prevent, which goes on in the ton suniption of fuel, and in certain processes of roasting or calcination in the smelting of metals. Roundly speaking, th, best designed steam engines and boilers require only half as much coal per horse power 'RI hula( as those less skilfully constructed, and the fuel unnecessarily consumed by had boiler furnaces is largely wasted as smoke through imperfect combustion. The utilization of blast furnaces gases for heat ing purposes, and the recovery of tar and am monia piodivc ' at the same time from the teal consumed in these furnaces, form an in stance of a double saving from the same source. In the report of the chief inspector of alkali corks for 1844, it is stated that the plant put up in recent years for collecting tar, ammonia, etc., at 57 Scotch blast furnaces cost $2.223.00n, sum fully equal to the cost of building the furnaces themselves. The condensing dues, miles in length. connected with some lead-smelt ing furnaces are modern examples for appli ances to condense lead fumes or vapor which formerly was allowed to escape, causine much foss of the metal.
Some instances of how waste in a solid form Irises in working rock and other mineral sub stances mots now be given In shaping and dressing granite paving stones as much as three fourths of the rock quarried is. in some in stances at least, wasted. This waste is yet only in very small part utilized for road metal, and for "granolithic• pavements Blast-furnace sag is now utilized in several ways, notably in the manufacture of Portland cement. In a number of cases the accumulations of other kinds of slag on the sites of ancient smelting works hare, in modern times, been again put through the furnace to extract metals left ht their, with profitable results. Some of the
refuse from the old silver mines of Lauri= has linen bought up by capitalises 'for thia•pur instance. though not of very recent date, may be given where, by the salvaging of a by-product, a fortune was very quickly amassed. About 1840 Mr. Askin of Birmingham dis covered a method of separating cobalt, in the form of oxide, from nickel, two metals which were very difficult to separate. This oxide of cobah was at first a waste product, but before very long it was put into the hands of potters, who readily bought it up to produce a blue color as their ware, at the rate of two guineas per pound. Among comparatively recent instances of utilization of by-products and waste products in the chemical industries, we may refer to the importance of the substances now developed from coal tar (q.v.), and the great value of some of them in the manufacture of dyes. Another example is the recovery of binoxide of manganese rn the production of chlorine for the manufacture of bleaching powder by WeltIon's beautiful process. Formerly for every 100 pounds of bleaching powder made about 100 pounds of the native oxide of manganese were required. Now this manganese is recov ered and used again and again in the process, with only a loss of about 5 per cent to make up each time it is returned to the chlorine still. The earlier methods of recovering manganese were not nearly so perfect, and, therefore, were not much used A process for the utilization of chemical waste on a great scale is Chance's method, patented hi 1888, of recovering sulphur from alkali makers' black-ash refuse. A British automobile manufacturing concern sal vages 1,200 gallons of cutting oil a week from scrap metal, this oil being used again with the addition of 10 per cent of new oil, the latter being the actual amount of unrecoverable waste. Another establishment treated in one year R3,400 pounds of lathe waste, recovering 2.292 gallons of cutting oil. Large quantities of machine oil are recoverable from rags and cotton waste used for wiping machinery. The process of oil recovery so cleanses the wipers that they are useful again. The year's report shows 350,000 wipers treated, and an annual replacement of only 15,000 new ckahs required; and a recovery of more than 5,000 gallons of oil —the total cost of the operation being less than $1,000.