Drop a little powdered ore in a test tube; add nitric acid; dilute with 1/8 water; warm gently over the spirit lamp. It may dissolve or it may not. In the latter case, add four times as much hydrochloric acid. Should all these attempts fail, a fresh sample must be taken, and equal parts of sodium carbonate and potassium carbonate added, and the whole strongly heated in a platinum crucible. The contents, after cooling, is dissolved in dilute nitric acid.
In any case the assay will now be dissolved, and will be in the solution. Filter. Pour ten drops into a test tube; add three or four drops of hydrochloric acid. A precipitate appears. It may be silver, lead or mercury. If silver, it grows dark violet after exposure to sunlight, or 30 or 40 drops of ammonia dissolves it in a few moments. Should it not dissolve, it is lead or mercury. Test for lead by filtering, and heating some of the precipitate on charcoal before the blow-pipe. A bead and yellow incrustation indicate lead. Should none of these things happen, then the metal is mercury. Filter; place in glass tubes; heat gently, and a mirror of quicksilver will appear on the sides of the glass.
This is as far as the prospector, without the various reagents and chemicals that the analyst has always at hand, will be able to go. More complex treatment must be reserved until a return to civilization.
CHAPTER III.
BLOW-PIPE TESTS.
BLOW-PIPE.
As a means of readily detecting the presence of minerals in their ores the blow-pipe, in the hands of a skillful operator, is unrivaled. Nor is this skill at all hard to come by; two or three weeks' patient study under a good master should teach a great deal, and subsequently proficiency would come by practice in the field. Unfortunately, some very clever men have become so enthusiastic as to blow-pipe work that they have devised methods by which the amount of metal in an ore as well as its nature may be determined, but in so doing have so enlarged the amount of apparatus, and complicated the tests so seriously that the simplicity of the blow-pipe outfit is in danger of being lost, and its chief advantage of being forgotten; for there are many better ways of determining the value of an ore. A good assay or, better still, a mill run, is worth incomparably more than any quantitative blow-pipe test, even when conducted by a Plattner.
The chemical blow-pipe is made of brass or German silver, with platinum tip.
The best fuel, taking everything into consideration, is a paraffin candle in cold climates, and a stearine candle in hot ones. Tallow may do in an emergency, but it requires too much snuffing.
