VALUABLE FLUX FOR THE BLOW PIPE. 



175 



lay Ihem for twelve hours in aquafortis, 

 and then three days in the juice of beets, 

 and they will become so soft that they 

 may be worked into any form. To 

 harden them again, lay them in strong 

 vinegar. Dioscorides says, that by boil- 

 ing ivory for the space of six hours with 

 the root of mandrogoras, it will become 

 so soft that it may be managed as one 

 pleases. 



Ivory-black, is the coal of ivory or 

 bone formed by great heat, while de- 

 prived of all access of air. 



The improved method of obtaining 

 ivory-black, is to calcine bones (and other 

 substances used for that purpose,) to black- 

 ness in air tight vessels, they are then 

 crushed in their dry state between metal 

 rollers, till they are sufliciently broken 

 to pass through a hopper into the eye of 

 a mill stone, by which they are reduced 

 to a line powder in the same manner as 

 corn is reduced to flour. The powder thus 

 obtained is then passed through a dressing 

 machine (constructed with brushes in the 

 usual way) the meshes of which are about 

 sixty-eight to an inch ; the part which 

 passes through it is fit for use and is 

 damped down with a small quantity of 

 water for sale; the remainder is returned 

 to the hopper and ground again. 



PROCESS OF MAKING THE SCHWEINFURT 

 GREEN DYE. 



One part of verdigris is to be dissolved 

 in a sufficient quantity of good vinegar, 

 by heat in a copper kettle. When it is 

 dissolved add to the same a solution of 

 one part of white arsenic in water. A 

 dusky green precipitate generally ensues, 

 which must be re-dissolved by the addi- 

 tion of more vinegar. This mixture is 

 novv to be boiled, when a granulated pre- 

 cipitate will be produced, of the most 

 beautiful green color, which after being 

 separated from the liquid (either by fil- 

 tration or by decanting after the color 

 has subsided,) is to be well washed and 

 dried, when it is ready for use either as 

 a dye or pigment. If the liquor, after 

 this process, should be found to contain 

 % more copper, more of the solution of 

 arsenic may be added, but if it contains 

 instead an excess of arsenic, then more 

 of the solution of copper may be added, 



completing the process as before men- 

 tioned. And if the liquid should contain 

 an excess of the acetic acid it may be 

 advantageously employed in the solution 

 of more verdigris. 



The color prepared by the preceding^ 

 process is of a bluish green; but as a 

 deeper and more yellowish green is fre- 

 quently required, this is obtained by dis- 

 solving a pound of common potash in 

 water to which add ten pounds of the 

 green color prepared by the former pro- 

 cess, and warm the mixture over a gentle 

 fire ; when the desired tint will be ac- 

 quired. If allowed to boil long, the color 

 will approximate in hue to Scheele's 

 green, nevertheless it is in all the tints of 

 greater brilliancy and beauty. The al- 

 kaline fluid that remains may be advan- 

 tageously employed in making Scheele's 

 green. — R^g- Jirt. Set. 



A CHEAP AND VALUABLE FILTERING 



MACHINE* may be constructed as follows: 

 Procure a large stone bottle with the 

 bottom knocked out, stop up the neck 

 partially with small stones, over these 

 form a layer of small pebbles then an- 

 other of gravel, increasing every layer 

 in fineness, and putting on, lastly, a stra- 

 tum of fine sand of the depth of several 

 inches. The sand, gravel, &c. should, of 

 course, be previously well washed, until 

 the water runs off clear and tasteless. 

 The upper stratum of sand is to be taken 

 out occasionally and washed, — ib. 



VALUABLE FLUX FOR THE BLOW PIPE. 



Takeof borax 1 ounce, nitre 2 drachms, 

 pounded flint glass 2 drachms, and cal- 

 cined horse's hoof half an ounce; these 

 are to be well fused together in a crucible, 

 taking care to add the horse's hoo( iasi, 

 and stirring it well with an iron spatula; 

 when it is quite fluid, pour it into cold 

 water, which will render it brittle, and 

 thereby it may be easily pulverized. It 

 is to be kept in well closed phials, free 

 from moisture, and the expense will be 

 very trifling, compared with its great 

 importance. — ib. 



* Alternate layers of charcoal' with the sand is an 

 improvement. 



