TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Preparation: The plasmagenic gas comprises a mixture of hydrogen fluoride (HF)-argon and/or hydrogen chloride (HC)l-argon containing 5 - 90%, more preferably 10 - 405, of argon. The segregated solidification is effected so as to separate solid silicon with less than 100 ppm of iron (Fe) from a liquid silicon rich in Fe. The re-melting is carried out in successive batches, and the re-fusion and plasma refining is effected in two separate furnaces.The plasma refining is effected with a gaseous mixture of HF-argon and/or HCl-argon containing 10 - 40% of argon. The first solidification, before plasma refining, is carried out with a front progression velocity less than 2x10 to the power -5 m/s. The second solidification after plasma refining is conducted with a front progression velocity less than 10 to the power -5 m/s, more preferably less than 5x10 to the power -6 m/s. The solidification operations are preferably carried out in a reverberatory furnace. The electric furnaces for re-melting and plasma refining are induction furnaces. The crucibles used for re-melting and plasma refining are of silica, carbon, graphite or silicon carbide. Prior to plasma refining, the liquid silicon is submitted to a batch vacuum treatment with injection of argon.Preferred Composition: The composition of the silicon comprises a total impurity content of 100 - 300 ppm, more preferably 100 - 150 ppm, boron content between 0.5 - 3 ppm, more preferably 0.5 - 2 ppm , a ratio between phosphorus content and boron content of 1 - 3 and a metallic element content less than 150 ppm, more preferably less than 70 ppm. The iron content is less than 20 ppm. EXAMPLE - From a production of silicon by a submerged electric arc furnace, a batch of 2 t of liquid silicon was sampled which gave an analysis of :- Fe : 0.24% ; Ca : 98 ppm ; Al : 245 ppm ; Ti : 240 ppm ; B : 32 ppm ; P : 19 ppm ; C : 19 ppm ; O : 1200 ppm. Part of the liquid silicon was poured into a silica ingot-mould of capacity 600 kg of silicon. The ingot, of surface area 2 m2, was then placed in a reverberatory furnace operating at 40 kW to obtain a solidification of 50% of the silicon in 1.25 hs.    After a waiting time of 75 minutes, the remaining liquid was poured off giving a 290 kg ingot. The remaining solid (294 kg) had an analysis of :- Fe : 94 ppm ; Ca : 24 ppm ; Al : 14 ppm ; Ti : 9 ppm ; B : 28 ppm ; P : 10 ppm ; C : 100 ppm ; O : 800 ppm. The operation was repeated several times to obtain a sufficient quantity of silicon of this quality. The silicon obtained was remelted in batches of 200 kg under an argon atmosphere in a 250 kW induction furnace operating at 1200 Hz, and starting with a base of liquid metallurgical silicon. Production of the first three batches was rejected.    Production of the following batches was transferred batch by batch for refining in a second induction furnace of similar capacity and characteristics, fitted with a plasma torch and supplied with a gaseous mixture of 75% hydrogen chloride (HCl) and 25% argon. The treatment time was 1 hour per batch. Each plasma-treated batch was then subjected to segregated solidification in 0.67 m squared ingots fitted with flow spouts, and placed in a heated reverberatory furnace at a power of 45 kW. The liquid was poured off after 3 hours giving a cooled ingot of 36 kg, and 162 kg of solidified silicon was recovered. The liquid gave an impurity analysis of :- Fe : 92 ppm ; Ca : 23 ppm ; Al : 14 ppm ; Ti : 9 ppm ; B : 8 ppm ; P : 10 ppm ; C : 50 ppm ; O : 80 ppm ; The solid obtained gave an analysis of :- Fe : 18 ppm ; Ca : 9 ppm ; Al : 8 ppm ; Ti : 5 ppm ; B : 8 ppm ; P : 10 ppm ; C : 50 ppm ; O : 90 ppm.