Pάrada.

Rasa.

Mercury, though not mentioned by Charaka* and Susruta, has in later days come to be regarded as the most important medicine in the Hindu Pharmacopoeia. Pάrada literally means that which protects, and mercury is so called because it protects mankind

* There is a passage in Charaka in the chapter on Kushtha or skin diseases which some physicians construe into a recommendation for the use of mercury.

It is this from all sorts of diseases. It is said that the physician who does not know how to use this merciful gift of God is an object of ridicule in society.

It may be translated as follows. Reduced mercury which cures all diseases should be taken by those affected with skin diseases. The term rasa, however, signifies mercury as well as many other things, such as myrrh, sulphur, gold etc., and since Charaka does not mention parada, the principal name for mercury, it is doubtful if he really meant mercury by the term rasa. Supposing, however, he did mean mercury, its use was at all evenly in his time, confined to skin diseases only.

Good mercury is said to be bright like the mid-day sun externally, and of a bluish tinge internally. Mercury of a yellowish-white, purple, or variegated colour should not be used in medicine. Mercury, as met with in commerce, contains several sorts of impurities, such as tin, lead, dirt, stone, etc. If administered in an impure state it is said to bring on a number of diseases; hence it is purified before use. Various processes for purifying mercury are described in books. At the present day the following is generally adopted by Kavirάjas. Mercury is first rubbed with brick-dust and garlic, then tied in four folds of cloth and boiled in water over a gentle fire for three-hours in an apparatus called Dolά yantra. When cool, it is washed in cold water and dried in the sun. Some practitioners use betle-leaves instead of garlic for rubbing the mercury with. Mercury obtained by sublimation of cinnabar is considered pure and preferred for internal use.1 Cinnabar is first rubbed with lemon juice for three hours, and then sublimed in the apparatus called Urddhapatana yantra. The mercury is deposited within the upper pot of the apparatus, in form of a blackish powder. This is scraped, rubbed with lemon-juice and boiled in water, when it is fit for use. A peculiar form of mercury called Shadguna bali jάrita rasa2 is thus prepared. A little sulphur is placed in an earthen pot, and over it some mercury. The pot is heated in a sand-bath, and, as the sulphur begins to melt, cautiously and gradually more of it is added to or placed over the mercury, altogether to the extent of six times the weight of the mercury. When the whole is melted like oil the pot should be quickly removed from the fire, and cooled till the mass is consolidated. It should then be broken, and the mercury extracted from within the mass. Mercury thus obtained is said to be superior to all other forms, but it is not much used at present.

The purified metal obtained by the processes above mentioned is employed for the preparation of mercurial compounds. Four preparations of mercury are described in books, namely, black, white, yellow, and red, called respectively, krishna, sveta, pita and rakta bhasrnas,

1. Krishna bhasma. The black preparation is the black sulphide of mercury, made by rubbing together and dissolving over the fire three parts of mercury with one of sulphur.l

2. Rasakarpura. The white preparation is the Rasakarpara or perchloride of mercury. Several processes are given for preparing it; one is as follows.2 Take of mercury and chalk equal parts, and rub them together till the globules disappear. Rub this mixture of chalk and mercury with pάnsu (salt obtained from saline earth) and the juice of Euphorbia nereifolia (snuhi) repeatedly. Enclose in a covered crucible and heat it within a pot full of rock salt. The perchloride of mercury will be deposited in the shape of a pure white powder under the lid of the crucible. The Bhάvaprakάsa gives the following process for its preparation.3 Take of purified mercury, gairika (red-ochre),brick dust, chalk, alum,rock salt, earth from ant-hill, kshάri lavana (impure sulphate of soda) and bhanda-ranjaka, or red earth used in colouring pots, in equal parts, rub together and strain through cloth. Place the mixture in an earthen pot, cover it with another pot, face to face, and lute the two together with layers of clay and cloth. The pots so luted are then placed on fire, and heated for four days, after which they are opened, and the white camphor-like deposit in the upper pot is collected for use.

3. Pita bhasma. The yellow preparation called Pita bhasma1 is directed to be prepared as follows. Take of mercury and sulphur equal parts, rub them together for seven days with the juice of bhumyάmalaki (Phyllanthus neruri) and hastisundi (Heliotropium Indicum). Place the mixture in a covered crucible, and heat it in a sand-bath for twelve hours. The result will be a yellow compound.

4. Rakta bhasma. The red preparation called Rakta bhasma or Rasa sindura2 is prepared in a variety of ways- The following is one of them. Take of mercury and sulphur equal parts, rub together with the juice of the red buds of Ficus Bengalensis (vata) for three days successively, introduce the mixture within a bottle and heat it in a sand-bath for twelve hours. A red deposit will adhere below the neck of the bottle. It is taken out in the shape of dark red shining scales.