SELENIUM. 



position to which he endeavours to establish the 

 British right of dominion over the circumjacent 

 seas. Some of the following years of his life were 

 occupied in Hebrew studies, the result of which 

 appeared in a work entitled De Jure Naturali et 

 Gentium juxta Disciplinam Ebraorum a valuable 

 but not very well digested repertory of all the 

 matter afforded by history or tradition, in relation 

 to the subject. In 1640, memorable for the meet- 

 ing of the long parliament, Selden was unani- 

 mously elected member for the university of Ox- 

 ford. His name appears on several committees, 

 appointed to inquire into abuses; but he neither 

 concurred in the prosecution of lord Strafford, nor 

 seemed desirous to abrogate the episcopal form of 

 church government, although anxious to check the 

 encroachments of ecclesiastical power. When the 

 differences between king and parliament were 

 manifestly tending to open hostilities, he opposed 

 the attempts of both parties to gain possession of 

 the sword, and, when he failed, withdrew, as much 

 as he was able, from public business. He remained, 

 however, with the parliament, and was one of the 

 synod which met at Westminster for the establish- 

 ment of church government. In 1643, he was ap- 

 pointed, by the house of commons, keeper of the 

 records in the Tower, and, the year following, sub- 

 scribed the solemn league and covenant. In 1645, 

 he was elected one of the twelve commissioners of 

 the admiralty; and, in 1646, the parliament voted 

 him 5000, as a reward for services. He continued 

 to sit in parliament after the execution of the king, 

 and employed all his influence for the protection of 

 learning. He refused to gratify Cromwell by writ- 

 ing an answer to the Eikon Basilike. He died in 

 1654. In private life, he was universally esteemed 

 for his goodness of heart and urbanity of manners; 

 and, as a scholar, he must be deemed one of the 

 most learned men of his day. His style is often 

 laboured and uncouth, although his speeches and 

 conversation were peculiarly luminous and clear. 

 Some opinion of the latter may be collected from 

 his Table Talk, published, after his death, by his 

 amanuensis. His library and museum were added 

 to the Bodleian library. His whole works were 

 collected in three folio volumes (usually bound in 

 six), by doctor David Wilkins (1726), with a life 

 of the author. See also Aikin's Life of Selden. 



SELENIUM; a new elementary body, detected 

 by Berzelius, in the sulphur of a sulphuric acid 

 manufactory, at Fahlun, in Sweden. The sulphur 

 was derived from iron pyrites, found at the copper 

 mine of Fahlun. After the combustion of the sul- 

 phur in the acid manufactory, there remained at 

 the bottom of the leaden chamber, a red or brown- 

 ish matter, which, when heated before the blow- 

 pipe, emitted a very strong odour, resembling that 

 of horse-radish. The name applied to this sub- 

 stance comes from vt^tivn, the moon, indicating its 

 relation to tellurium. The purification of the 

 selenium, as found above, is a tedious process; it 

 being mingled with no fewer than eight foreign 

 substances. When pure, however, it exhibits the 

 following properties: Exposed to a heat higher 

 than that of boiling water, it melts, and on cooling 

 becomes solid: in this state, it has the metallic 

 lustre, a deep brown colour, and a conchoidal frac- 

 ture. The powder of selenium is a deep red. In 

 very thin slivers, it is transparent, with a ruby-red 

 colour. It crystallizes with difficulty in cubes or 

 four-sided prisms, terminated by pyramids, specific 

 gravity, 4-3. It is easily scratched by the knife; 



is brittle, and readily reduced to powder. When 

 heated in a retort, it begins to boil at a temperature 

 below that of a red heat, and assumes the form of 

 a dark-yellow vapour, not so intense as the vapour of 

 sulphur : the vapour condenses in the neck of the re- 

 tort in black drops, which unite into larger drops, as 

 in the distillation of mercury. Selenium is a very bad 

 conductor of heat, and a non-conductor of elec- 

 tricity. It combines with three portions of oxygen, 

 forming three separate compounds ; viz. oxide of 

 selenium, selenious acid, and selenic acid. The first 

 of these is formed whenever selenium is strongly 

 heated in the open air, and is distinguished by the 

 smell above alluded to. It is not absorbed by 

 water, nor is it capable of uniting with acids. 

 Selenious acid may be formed by burning selenium 

 in oxygen gas, or by heating it in contact with 

 nitric acid, or nitro-muriatic acid. When the solu- 

 tion cools, the selenious acid is deposited in large 

 prismatic crystals, longitudinally striated, and 

 similar to those of nitrate of potash. Its vapour 

 resembles, in colour, chlorine gas. Its taste is 

 acid, and it leaves a slightly burning sensation upon 

 the tongue. It is very soluble in water and in 

 alcohol. Selenious acid consists of selenium 100 

 and oxygen 40-43. Selenic acid is formed by deto- 

 nating an intimate mixture of one part of selenium 

 and three of nitre, in small quantities at a time, in a 

 red-hot crucible. The residue, which contains 

 seleniate of potash, is to be dissolved in water, and 

 nitrate of lead added to the neutralized solution 

 till all the selenic acid is thrown down in the state 

 of seleniate of lead. This powder is carefully 

 washed, diffused in water, and a current of sul- 

 phureted hydrogen gas passed through it till the 

 whole lead is converted into sulphuret. The liquid 

 being now filtered and heated to expel the sul- 

 phureted hydrogen gas, the result is an aqueous 

 solution of selenic acid. It may be concentrated 

 by evaporation till its temperature reaches 536; 

 but if the heat is raised higher, oxygen gas is 

 given out, and the acid changed to the selenious. 

 Its specific gravity is 2-6. It resembles sulphuric 

 acid in its consistence, and in the heat evolved 

 when it is mixed with water. It contains about 

 16 per cent, of water. The acid is composed of 

 selenium 100 and oxygen 60-66. Thus it appears, 

 that the selenious and selenic acids resemble sul- 

 phurous and sulphuric acid in their constitution. 

 Chlorine and selenium appear to combine in two 

 different proportions, and to form a chloride and a 

 bichloride; the former of which is liquid, and the 

 latter solid. No experiments have been made to 

 determine the nature of the combinations of selenium 

 with iodine and fluorine. Selenium combines with 

 hydrogen, and forms a gaseous substance, which has 

 been distinguished by the name of selenieted hydro- 

 gen gas. When selenium and potassium are fused 

 together, a compound is formed, which dissolves in 

 water : the liquid has the colour of beer. When 

 muriatic acid is added, a considerable proportion of 

 the selenium is precipitated, and the liquid acquires! 

 the smell of sulphureted hydrogen. When muriatic 

 acid is poured upon this concentrated fluid in a 

 retort, the seleniet of potassium becomes red, an 

 effervescence takes place, and selenieted hydrogen 

 gas is driven off. The gas is colourless, and is 

 possessed of an odour like sulphureted hydrogen ; 

 but it speedily acts with great energy upon the 

 organs of smell and the throat, occasioning a painful 

 feeling, destroying the sense of smell, and producing 

 a severe cough. It is more soluble in water than 



