Arka are distilled essences, which contain the volatile Constituents of the drugs used in the preparation, in a medium of water and they are equivalent to the aquae’ or ‘waters’ Of the Western Pharmacopoeia, which are prepared in the same.
Arka are prepared by a process of distillation of water-Soaked-raw drugs. The volatile principles which are evolved admixtured with water vapour are condensed and taken.
1. The essential drugs from which the arka is to be Obtained.
2. Bottles of large capacity for collection of the distillate.
3. An assembly of apparatus as described below or Modifications thereof for distillation. (The commonest type in use is being described here, with some suggestions for Improvement of the apparatus which will facilitate efficient Distillation of the medicine.)
Apparatus for distillation
The still consists of a basal receptacle to contain the Drugs, and a cover with, an exhaust tube which is conveniently Bent to drain the distillate into the bottle. A cupuiar reservoir Is provided at the region where the exhaust leaves the lid portion.
The receptacle of the retort may be an earthern pot or preferably a metallic one. When made of metals like brass or Copper, the interior is tinned. Iron should not be used because It gets rusted and corroded in a short period. Stainless steel Stills are excellent. It is advisable to provide a perforated false bottom in the receptacle to keep the drug intended for extraction To avoid charring. The cupuiar reservoir over the lid is filled With cold water during distillation and it serves as a sort of A crude type condensor. This crude device could be replaced by a good condenser in the form of a water jacket around The exhaust tube. Or even a spiral type of condenser could Be provided. Good condensers ensure complete condensation Of the vapours and thereby the quality is ensured. Cold water Should be circulated continuously through the condenser during distillation.
Process of preparation
The drugs are crushed into coarse particles and soaked In the prescribed quantity of water for about 24 hours and Then put along with the water into the still for distillation. The lid is tightly placed and sealed around to prevent Vapours from escaping. For the purpose of sealing, a cloth ribbon with a, paste of black gram is used. Heat is applied To the drug mixture and the distillate is collected in large bottles and mixed well to ensure uniform concentration of the medicine because the first distillate is ranch concentrated MH compared to that collected at the end of the process when the drugs are depleted of the medicinal principles. A continuous water current should be maintained in the condensor. When a cupuiar type of condenser is used, water is replaced by cool water as and when it becomes warmed up. The vessel or bottle in which the distillate is collected is also plticed in a trough containing cold water. (In large scale preparation, large stills which are heated by super-heated ttoam are employed for distillation).
The end of the process of preparation is marked by the encape of dark fumes, from the exhaust. Further attempts to Heat and collect the remnants of condensate should not be made once this phenomenon is noticed. Usually the volume of the distillate is 70% of the total volume of the drug and water mixture taken for distillation. The whole of tho distillate should be mixed to make a preparation of uniform concentration.
Storage and usage of Arka
Arka should be stored in tightly stoppered glass bottles. Any arka if kept open and exposed to air will lose its volatile medicinal principles. Some physicians remove tho oil drops in the arka and consider the oil as undesirable. Usually, the bottle is well shaken before use to mix the oil droplets with the arka. These oil droplets are in reality medicinally important.
Arka are mixed with, equal quantity of water before use.