PART II. DIVISION I. APPARATUS REQUIRED FOR PHYTO-CHEMICAL ANALYSES. : THESE will be described under the following heads : A. Weighing apparatus. B. Drying apparatus. C. Comminuting apparatus. F. Evaporating apparatus. G. Miscellaneous apparatus. A.-WEIGHING APPARATUS. Three different balances are required for use:-A so-called weigh-bridge to carry 50 kilograms, and to turn with 10 grams or less, when so loaded; a common balance, which indicates distinctly 1 decigram when carrying 1 kilogram in each pan; and a chemical balance to carry 50 grams, and to turn, thus loaded, with 1 milligram. For better security of dust, fumes, &c., the lastnamed balance is always to be kept in a glass case. The weights, now in common use amongst analytical chemists, are made according to the French or metrical system, and consist of brass or German silver. Only the smaller weights, from 1 decigram downwards, are made of aluminium. To use platinum for this purpose is inconvenient, on account of the smallness of the pieces, and the risk of losing them. The weights, and especially those under 5 grams, are never touched with the bare fingers, but with pincers made of metal. B.-DRYING APPARATUS. Freshly-gathered plants or parts of plants are freed from adhering impurities, as earth, sand, or dust, by beating, dusting, or quickly washing with water. Thick roots, stems, branches, or fleshy fruits, are first split or cut into pieces of a proper size, and afterwards spread on wooden sieves, previously covered with printing paper, and thus exposed on warm days to the action of the air and the diffused sunlight, or, if the temperature should be below 10°, they are dried by artificial heat not exceeding 40°, but carefully screened from steam and smoke. The drying is finished, and the so treated substance called air-dried, when it does no longer incur loss of weight. With the exception of certain succulent fruits, which on drying undergo a partial decomposition, all vegetable substances are submitted to analysis air-dried. To estimate the water still retained by the air-dried material, a small sample of the latter is properly comminuted as described under C., and intimately mixed. Two to five grams of the substance thus treated are then put into a platinum crucible, and the latter placed into an air-bath made of copper, and provided with a thermometer. The whole apparatus is now heated to a temperature of 110° to 120° by means of a small spirit (or gas) lamp. (For particulars see Div. III., 1.) Vegetable substances in the natural state less than those educts, obtained in the course of the analysis, and which, on account of their liability to decompose under the influence of heat, atmospheric air, or moisture, cannot be dried in the air-bath, must have the last traces of water removed under the jar of the air-pump with the simultaneous application of water-absorbing substances, such as quicklime, fused chloride of calcium or concentrated sulphuric acid, any of which are placed close to the substance in question, under the receiver of the air-pump. C.-COMMINUTING APPARATUS. Thick or woody roots, stems or large branches, are at first thinly split with an axe; the single pieces are then cut up transversely on the cutting-board and separated by means of a sieve of wire gauze, with apertures not larger than one-sixth of an inch; the coarser parts are further comminuted in the stamping-box by means of cross-knives provided with a long handle, and again passed through the sieve. To reduce vegetable parts of this kind to a still finer or powdery state, will generally require much time and labour, but this is essential for a satisfactory final result. Often the operation is greatly facilitated by successively exposing the substance to a gentle heat and then pounding it in a metal mortar. Tough hard woods, after being fastened in a screw-vice, may be advantageously rasped by means of a coarse file. This is a good but rather tedious process. Flexible or thin roots are placed at once on the cutting-board; still thinner ones only into the stamping-box, and afterwards, if necessary, into the mortar. Fresh and succulent roots are split with a knife of horn or of a metal unaffected by the acid juices, first lengthwise, and then transversely. Woody stems and thick branches are treated like roots; thinner woody stalks are first cut on the board, afterwards stamped in the box; very thin ones go at once into the stamping-box. Barks may be reduced to powder in the iron mortar, but those with a tough fibrous bast are first treated on the cutting-board. Fresh herbaceous stalks are bruised in a stone mortar. The material of the latter must be possibly pure sandstone; marble would be affected by the always acid juice. Fresh leaves or flowers are bruised in the stone mortar; dry ones are stamped in the box. Succulent fruits or coverings of seeds are bruised in the stone mortar, but if large they are previously cut into pieces with the horn knife. Ordinary dry fruits are pounded in the iron mortar, but require, when tough, to be dried at a very gentle heat. Seeds are treated like dry fruits; those rich in oil, to prevent the latter from separation, are first broken in the iron mortar and then submitted to a moderate trituration. Should it be possible to separate the pericarps from the seeds, this may be conveniently effected either with a hammer or in the iron mortar, and each part is then examined by itself. D.-EXTRACTING APPARATUS. Glass and porcelain vessels would answer this purpose best, but very large vessels of those materials are easily broken, and consequently costly. As a substitute the chemist generally employs tin or copper vessels, especially when working with large quantities. Glass flasks are required, of various sizes from the smallest up to those of two litres capacity. The glass of these fiasks must be of a uniform thinness, and the edges of their necks must be bent outwards, to allow the insertion of a cork stopper without risk of cracking. Infusion-pots with lids, both made of porcelain, may be used for the extraction of substances containing no volatile matters, with either water, diluted acids, or diluted alkalies. A tin still is further required, capable of holding at least 10 litres of water, with head and worm of the same metal. A still of |