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Other birds have acquired long beaks to penetrate the moister soils in search of insects or roots, as woodcocks; and others broad ones to filtrate the water of lakes, and to retain aquatic insects.
We found at his dwelling large earthen pots for boiling the vegetable juice, shallower vessels to favour the evaporation by a larger surface, and leaves of the plantain-tree rolled up in the shape of our filters, and used to filtrate the liquids, more or less loaded with fibrous matter. The greatest order and neatness prevailed in this hut, which was transformed into a chemical laboratory.
Collect the solution in the beaker in which precipitation took place. Wash the precipitate twice by decantation, and finally transfer it to the original filter. The filtrate and washings are combined with those from the first precipitation and treated for the determination of sulphur, as prescribed on page 112.
Boil for two minutes; allow the precipitated calcium oxalate to settle for a half-hour, and decant through a filter. Test the filtrate for complete precipitation by adding a few cubic centimeters of the precipitant, allowing it to stand for fifteen minutes. Redissolve the calcium oxalate in the beaker with warm hydrochloric acid, pouring the acid through the filter.
Any magnesia present in the filtrate of the oxalate of lime is by the addition of a solution of phosphate of soda separated as phosphate of ammonia and magnesia, after having stood twenty-four hours. The precipitate is filtered off, washed with water to which a little chloride of ammonia is added, dried, and after calcining the fiber and adding the filter ash, glow heated in the crucible.
Solutions should be filtered while hot, as far as possible, since the passage of a liquid through the pores of a filter is retarded by friction, and this, for water at 100°C., is less than one sixth of the resistance at 0°C. When the filtrate is received in a beaker, the stem of the funnel should touch the side of the receiving vessel to avoid loss by spattering.
In a laboratory experiment, made at college it was shown that when raw phosphate was shaken with water and then filtered, the filtrate contained practically no dissolved phosphorus; but, if a dilute solution of such salts as exist in kainit was used in place of pure water, then the filtrate would contain very appreciable amounts of phosphorus.
Cool the filtrate to approximately the standard temperature of the laboratory, and transfer it to a 250 cc. measuring flask, washing out the beaker thoroughly.
Taking 200 gr. of ore from a sample assaying 17 oz. fine gold per ton, grinding it finely and heating for some hours with yellow sodium sulphide on decomposing the filtrate and treating for gold I got a result at the rate of 12 oz. per ton. This was repeated several times with the same result.
Wash the filter five times with water, and finally pour through it aqueous ammonia. Filter off the calcium oxalate upon the filter first used, and wash free from chlorides. The filtrate should be made barely acid with hydrochloric acid and combined with the filtrate from the first precipitation. Begin at once the evaporation of the solutions for the determination of magnesium as described below.
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