English Name

Silver metal

Definition

Rajata (Ag) is a silver- white metal available in the form of ingots.

Synonyms

Samskrta : Candra, Raupya, Tāra, Rūpyaka, Rūpya, Rūpyamala

Regional Name

Bangali - Rūpā, English - Silver, Gujarati - Rūpum, Cāndī, Hindi - Cāndī, Rūpā, Latin - Argentum, Marathi - Cāndī, Rupe, Telugu - Vendi

Broad Classification

Metal

Origin and occurrence:

Rajata occurs in nature in the free state, occasionally 99% pure, but generally containing copper, gold and other metals. Native Rajata occurs in the earth's crust in two principal ways: (i) as small amounts in the oxidised zone of ore deposits and (ii) as deposits from hydrothermal solutions. It occurs with sulphides, zeolites, calcite, barite, fluorite and quartz. Native Rajata is much rare in occurrence than native Svar´a but is widely distributed in small amounts. In recent years, much of the total Rajata production has been obtained as by-product of gold refining. It is obtained from its ores mainly by amalgamation with mercury or by cyanidation if present in a finely divided state. If not finely divided, the ores are concentrated and smelted. But largely Rajata is derived from smelting of Lead, Zinc and Copper ores which are argentiferous. Pure Rajata may contain Svar´a (Au) up to 10% with trace amounts of Cu and sometimes Pt, Sb, Bi, As and Hg. In India, there are no Rajata deposits as such. It is found associated mainly with lead and zinc and to some extent with copper and gold. All galena (lead ore) deposits of Zawar, Rajpura-Dariba, Deri-Basantgarh and Rampura-Aghucha in Rajasthan, Sargipalli in Orissa, Zangamarajupal, Bandalamotu and Nallakonda in Andhra Pradesh, Hesatu-Belhathan in Bihar and Pauri-Garhwal in Uttaranchal invariably contain Rajata. It is available in market in the form of ingots.

Physical Properties

Nature : Granular, nuggets and feather like dendrites, Colour : Silver white, turning greyish black due to, tarnishing, Streak : White, Cleavage : None, Fracture : Hackly, Lustre : Metallic, Tenacity : Sectile, ductile and malleable, Transparency : Opaque, Hardness : 2.5 to 3.0, Sp.Gr : 10.1 to 11.1

Chemical Properties:

Reaction with Acids: Prepare solution of Rajata in nitric acid and add hydrochloric acid to it. A dense white curdy precipitate of silver chloride is produced. This precipitate is soluble in ammonia. Solubility: Soluble in nitric acid. Assay: Rajata should contain not less than 98.5% Silver (Ag) when analysed by A. A. S. (Appendix-3.2.1). Heavy metals and Arsenic: In Rajata Mercury, Lead, Arsenic and Cadmium should be absent. Other Elements: May contain the following within ± 20% of the stated limits:- Copper = 1.40 %, Sulphur = traces and Gold = 0.001% (Appendix-3.1 & 3.2).

Śodhana

Shall not be used in formulations without subjecting it to śodhana. Rajata is used in the form of bhasma, the details of which are given in the monograph of bhasma.