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Instantaneous Positive Paper

Mix 6 drachms of a saturated solution of undecompounded bodies, which are bichloride of mercury with 1 pint distilled water. Float the paper on this solution in a distinguished by their weight, lustre, fusibility, flat dish. Dry it; take into a dark place lit power of conducting heat, electricity, &c. of conducting heat, clectricity, &c. by a candle with a yellow glass, and render it (see Nos. 3349 to 3357 inclusive), and the sensitive by a solution of 38 grains nitrate of numerous c compounds which they furnish by silver to 1 ounce water. To print, expose to combination with one another, and with other a perpendicular light from 2 to 10 seconds in bodies. When their solutions are decomposed summer, about 1 minute in winter; then by a galvanic current, the metals always apcurrent, the metals always apimmediately cover with a black cloth. The pear at the electro-negative surface, and are image, at first very feeble, is developed by hence termed electro-positive bodies. electro-positive bodies. this solution; sulphate of iron, 15 grains; 3187. Assaying. The method of de- Assaying. The method of deglacial acetic acid, 25 grains; distilled water, termining the quantity of pure gold and silver 1 ounce. The deepening of tint must be in the alloys of these metals. This art reof these metals. This art rewatched, and arrested at the proper moment. quires great skill and experience m its perand experience in its per- Then wash, and fix with hyposulphite. formance; and, from the costliness of the

3178. Albumenized Paper for Posi- precious metals, is of the utmost importance. tive Printing. White of egg, and water, A downward. draught furnace of any shape equal parts; iodide of potassium or chloride and size may be employed, provided it will of sodium, 5 grains to 1 ounce water (or bro- afford a sufficient heat, and allow the introsufficient heat, and allow the intromide of potassium, 20 grains). Coat the paper duction of the muffle. The muffle is a pot with this solution. Dry. Immerse in the made of clay, and furnished with an opening dark in bath of 120 grains nitrate of silver to at its end, to admit the introduction of the 1 ounce water. Dry again. This is exposed cupels, and to allow of inspection of the proof inspection of the prowith the negative over it, for 10 to 15 minutes. cess. It is placed on the muffle-plate, by