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the oxidised ores. It has also been pointed out that the slag from any extraction has half the value of the metal.
(e) Extraction of mercury : -The mercury ore is kept in a closed furnace and covered with dried cowdung cakes. On heating the furnaces with slow blasts, mercury comes out as sublimate and collected on the top of the furnace. 2. Preparation of some common alloys
(a) Brass :-It is prepared by fusing one part of copper with a fusion mixture containing four parts of Dhavadia and two parts of jaggery (here dhavadia must contain zinc compounds which are reduced to zinc metal by the reducing property of the jaggery) in a furnace. The brass so obtained is ideal brass. Other qualities of brasses may also be obtained by increasing the quantity of copper during fusion. It is now known that brass is a mixture of copper and zinc in varying proportions and a variety of brasses are possible.
(b) Bronze :--The bronze is a mixture of copper and tin in various proportions. In Pheru's days, it was made by boiling one part of tin obtained from the treatment of solder metal with four parts of copper.
(c) Solder :- It seems that this alloy was prepared directly from some ore, heating it with kommans powder. The process gave a hot flowing liquid metal called Cambia which was used for making bronze as above. 3. Preparation of some Compounds
(a) Hingul :- This is called cinnabar today. It is prepared by heating sulfur and mercury in the ratio of 1:4. On current knowledge, the ratio should be 32:200. There is mention of preparing the compound by heating the powder of realgar and orpiment together for three days continuously. It seems these compounds arsenic must be containing mercury in some form which forms hingul after complete elimination of arsenic during long heating.
(b) Sindüra or red lead :- This is prepared in two stages. In the first stage the lead metal is fused with 5% ashes of bamboos making the metal perchance in soluble form. The mass is then dissolved in water and filtered hot. The filtrate is allowed to settle and after decantation, it is ground and heated strongly in a furnace upto three days when its color changes to deep red, If heated too strongly, it is again converted to lead metal. 4. Some other useful description
Besides the coinage metals and some of their compounds, there are descriptions about the units of weights used for these metals as below:
16 yavas = 1 masha = l vanni 4 māsās=1 tanka
3 tānkas=1 tola = 11.55 gms. which gives the least unit of yava as equivalent to 0.057 gm.
There is description of various types of coins in use in various parts of the country at that time. This includes their composition and values. Some classes of coins are given in Table 11.
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