BRAZIL NUTS, the seeds of Bertholletia excelsa, a gigantic tree belonging to the natural order Lecythidaceae, which grows in the valleys of the Amazons and generally throughout tropical America. The tree attains an average height of 130 ft., having a smooth cylindrical trunk, with a diameter of 14 ft. 50 ft. from the ground, and branching at a height of about 100 ft. The lower portion of the trunk presents a buttressed aspect, owing to the upward extension of the roots in the form of thin prop-like walls surrounding the stem. The fruit of the tree is globular, with a diameter of 5 or 6 in., and consists of a thick hard woody shell, within which are closely packed the seeds which constitute the so-called nuts of commerce. The seeds are triangular in form, having a hard woody testa enclosing the “kernel”; and of these each fruit contains from eighteen to twenty-five. The fruits as they ripen fall from their lofty position, and they are at the proper season annually collected and broken open by the Indians. Brazil nuts are largely eaten; they also yield in the proportion of about 9 oz. to each ℔ of kernels a fine bland fluid oil, highly valued for use in cookery, and used by watchmakers and artists.
BRAZIL WOOD, a dye wood of commercial importance, obtained from the West Indies and South America, belonging to the genera Caesalpinia and Peltophorum of the natural order Leguminosae. There are several woods of the kind, commercially distinguished as Brazil wood, Nicaragua or Peach wood, Pernambuco wood and Lima wood, each of which has a different commercial value, although the tinctorial principle they yield is similar. Commercial Brazil wood is imported for the use of dyers in billets of large size, and is a dense compact wood of a reddish brown colour, rather bright when freshly cut, but becoming dull on exposure. The colouring-matter of Brazil wood, brazilin, C16H14O5, crystallizes with 1½ H2O, and is freely soluble in water; it is extracted for use by simple infusion or decoction of the coarsely-powdered wood. When freshly prepared the extract is of a yellowish tint; but by contact with the air, or the addition of an alkaline solution, it develops a brick-red colour. This is due to the formation of brazilein, C16H12O5·H2O, which is the colouring matter used by the dyer. Brazilin crystallizes in hexagonal amber yellow crystals, which are soluble in water and alcohol. The solution when free of oxygen is colourless, but on the access of air it assumes first a yellow and thereafter a reddish yellow colour. With soda-ley it takes a brilliant deep carmine tint, which colour may be discharged by heating in a closed vessel with zinc dust, in which condition, the solution is excessively sensitive to oxygen, the slightest exposure to air immediately giving a deep carmine. With tin mordants Brazil wood gives brilliant but fugitive steam reds in calico-printing; but on account of the loose nature of its dyes it is seldom used except as an adjunct to other colours. It is used to form lakes which are employed in tinting papers, staining paper-hangings, and for various other decorative purposes.
BRAZING AND SOLDERING, in metal work, termed respectively hard and soft soldering, are processes which correspond with soldering done at high and at low temperatures. The first embraces jointing effected with soldering mixtures into which copper, brass, or silver largely enter, the second those in which lead and tin are the only, or the principal, constituents. Some metals, as aluminium and cast iron, are less easily soldered than others. Aluminium, owing to its high conductivity, removes the heat from the solder rapidly. Aluminium enters into the composition of most of the solders for these metals, and the “soldering bit” is of pure nickel.
The hard solders are the spelter and the silver solders. Soft spelter solder is composed of equal parts of copper and zinc, melted and granulated and passed through a sieve. As some of the zinc volatilizes the ultimate proportions are not quite equal. The proportion of zinc is increased if the solder is required to be softer or more fusible. A valuable property of the zinc is that its volatilization indicates the fusing of the solder. Silver solder is used for jewelry and other fine metal work, arid has the advantage of high fusing points. The hardest contains from 4 parts of silver to 1 of copper; the softest 2 of silver to 1 of brass wire. Borax is the flux used, with silver solder as with spelter.
The soft solders are composed mainly of tin and lead. They occur in a large range. Common tinner’s solder is composed of equal parts of tin and lead, and melts at 370° Fah. Plumber’s solder has 2 of lead to 1 of tin. Excess of lead in plumber’s solder renders the solder difficult to work, excess of tin allows it to melt too easily. Pewterers add bismuth to render the solder more fusible, e.g. lead 4, tin 3, bismuth 2; or lead 1, tin 2, bismuth 1. Unless these are cooled quickly the bismuth separates out.
The essentials of a soldered joint are the contact of absolutely clean surfaces, free from oxide and dirt. The surfaces are therefore scraped, filed and otherwise treated, and then, in order to cleanse and preserve them from any trace of oxide which might form during subsequent manipulation, a fluxing material is used. The soldering material is compelled to follow the areas prepared for it by the flux, and it will not adhere anywhere else. There is much similarity between soldering and welding in this respect. A weld joint must as a rule be fluxed, or metal will not adhere to metal. There is not, however, the absolute need for fluxing that there is in soldered joints, and many welds in good fibrous iron are made without a flux. But the explanation here is that the metal is brought to a temperature of semifusion, and the shapes of joints are generally such that particles of scale are squeezed out from between the joint in the act of closing the weld. But in brazing and soldering the parts to be united are generally nearly cold, and only the soldering material is fused, so that the conditions are less favourable to the removal of oxide than in welding processes.
Fluxes are either liquid or solid, but the latter are not efficient until they fuse and cover the surfaces to be united. Hydrochloric acid (spirits of salts) is the one used chiefly for soft soldering. It is “killed” by the addition of a little zinc, the resulting chloride of zinc rendering its action quiet. Common fluxes are powdered resin, and tallow (used chiefly by plumbers for wiped joints). These, with others, are employed for soft solder joints, the temperature of which rarely exceeds about 600° Fah. The best flux for zinc is chloride of zinc. For brazed joints, spelter or powdered brass is employed, and the flux is usually borax. The borax will not cover the joint until it has been deprived of its water of crystallization, and this is effected by raising it to a full red heat, when it swells in bulk, “boils,” and afterwards sinks quietly and spreads over, or into the joint. There are differences in details of working. The borax is generally powdered and mixed with the spelter, and both with water. But sometimes they are applied separately, the borax first and over this the particles of spelter. Another flux used for copper is sal ammoniac, either alone or mixed with powdered resin.
As brazed joints often have to be very strong, other precautions are frequently taken beyond that of the mere overlapping of the joint edges. In pipes subjected to high steam pressures, and articles subjected to severe stresses, the joints are “cramped” before the solder is applied. That is, the edges are notched in a manner having somewhat the appearance of the dovetails of the carpenter; the notched portions overlap the opposite edges, and on alternate sides. Such joints when brazed are stronger than plain overlapping joints would be. Steam dome coverings are jointed thus longitudinally as cylinders, and the crown is jointed thereto, also by cramping. Another common method of union is that of flanges to copper pipes. In these the pipe passes freely within a hole bored right through the flange, and the solder is run between. The pipe is suspended vertically, flange downwards, and the spelter run in from the back of the flange. The fused borax works its way in by capillary action, and the spelter follows.