SODIUM. 



Dr. Pcarfon firft prepared it artificially, and introduced 

 it into medicine as a purjrative. He dilFolved 1400 grains of 

 cryitallized carbonate of foda in 2100 grains of water, and 

 added gradually joo grains of phofphoric acid, of the fpeci- 

 fic gravity i . 85. Tliis folution he boiled for a few minutes, 

 and filtered it while hot. The folution was fet out in a cool 

 place to cryftallize. 



This fait is often made by faturating foda with the fuper- 

 phofphate of lime obtained from bones by fulphuric acid, 

 and is never fufBciently free from lime. 



The acid (hould be obtained by burning phofphorus, and 

 the foda ufed in the ftate of well-formed cryftals, when the 

 pure fait is required. 



It cryftallizes in the form of rhomboidal prifms, termi- 

 nating with three-filled pyramids. 



It efflorefces by expofure to the air. 



Its taile is very like muriate of foda, but more mild and 

 agreeable. 



It is foluble in four parts of cold, and in about three parts 

 of boiling water. 



When expofed to heat it firft undergoes the watery fufion. 

 When heated to rednefs, it melts into a white enamel. From 

 this property it has been propofed as a fubftitute for borax, 

 in the foldering of metals : it alfo refembles the fame fub- 

 ftance in forming coloured glaffes with metallic oxyds. 



It is partially decompofed by the fulphuric, nitric, and 

 muriatic acids, leaving it in a ftate containing double its ori- 

 ginal quantity of acid. This is called the fuperphofphate of 

 foda. It was this fait which Prouft took for a peculiar 

 acid. It is more foluble in water than the phofphate, and 

 does not eafily cryftallize. 



Phofphate of foda has not been analyfed : fince, how- 

 ever, the weight of an atom of phofphorus is 13, and phof- 

 phoric acid 13 -t- 2 X 7.5 = 28, then phofphate of foda 

 will be 2 X 28 -f 59, or 



Soda 

 Acid 



51 



49 



100 



Fluate of Soda. — This fait may be formed by adding 

 fluoric acid to carbonate of foda, till the effervelcence 

 ceafes. 



On evaporation, it forms into cubic cryftals. Thcfe are 

 fparingly foluble in water, and have an aftringeiit bitter 

 tafte. 



Borate of Soda. — This is a fait with half the quantity of 

 acid which the borate contains ; it is known in commerce 

 and in the arts by the name of borax. The latter fubftaiice 

 is extrafted from a fubftance called tincal : the true borate 

 is, therefore, not ufed, but the fub-borate or borax. 



Suh-borate of fodaxi cryftalljzed in hexagonal prifms, with 

 two fides broader than the reft. It is femitranfparent. 

 Its fpecific gravity is 1.74. It is foluble in twelve parts 

 of cold water, and in fix of boiling water. It has a fweetifti 

 tafte, and rather alkaline. When expofed to the air, it is 

 foon reduced to a white powder, with much lofs of weight. 

 This arifes from the efcape of the water of cryftallization. 

 Artifts are apt to ufe it too plentifully in this ftate, and 

 fancy that its proper virtue is gone ; but the white powder 

 is equally valuable with the fait for all purpofes. When 

 the fame change is bro.ught about by heat, the borax is faid 

 to be calcined. If a ftrong heat be given to it in a cru- 

 cible, it melts into a tranfparent glafs. It is frequently 

 ufed in forming choice fpecimens of (ham cryftals, by fufion 



with flint, lead, and manganefc. The compofition of borax, 

 according to Bergman, is, 



I 



Acid 

 Soda 



Water 



39 

 '7 



44 



The acid i^ obtained from this f:ilt by diflolving it in hot 

 water, and then adding fulphuric acid. As the liquid 

 cools, fmall fcaly cryftals are precipitated, which are the 

 pure boracic acid. 



The bafe of this acid has been difcovered fince the com- 

 mencement of this work, and even fince this acid has been 

 treated of : we, therefore, feel it our duty to give fome ac- 

 count of it here. 



When boracic acid, flightly moiftened, is expofed be- 

 tween two plates of platina, one being connefted with the 

 copper fide of a Galvanic battery, and the other with the 

 zinc fide, the oxygen of the acid is attrafted to the zinc 

 or pofitive fide, and the inflammable bafe to the copper or 

 negative fide. This is a dark coloured fubftance, which be- 

 comes detached from the reit of the mafs, and is the bafe in 

 qneftion. This experiment was firft made by fir Humphrey 

 Davy, in March 1808, about the time that he difcovered 

 potaflium and fodium. In the November following it ap- 

 pears that he, as well as Meftrs. Gay Luftac and Thenard, 

 obtained this bafe by heating boracic acid with potaflium. 

 The latter chemift alfo fucceeded in recompofing the acid. 

 This fubftance has been called boron by fir Humphrey 

 Davy, which name it itill retains. 



Boron is an opaque fubftance of a dark olive colour. 



It is not fufible or volatile at any known temperature. 

 When heated in the open air, it burns by abforbing oxygen, 

 and is converted into drj' boracic acid. In pure oxygen 

 gas it undergoes more vivid combuftion, giving out bright 

 fcintillations. The ma(s becomes coated with boracic acid, 

 and the remainder of the bafe is found unchanged in the 

 cruft. 



It is a non-conduftor of eleftricity, a proof that it is not 

 of a metallic nature. 



It is infoluble in water. 



The proportion of oxygen in boracic acid is not yet 

 known. The cruft of boracic acid, which forms on boron 

 vvlieii it is burned, fecures the remainder from the oxygen, 

 fo as to render the refult ambiguous. 



Sir Humphrey Davy judges, from the quantity of po- 

 taflium required for the decompofition of the acid, that it 

 contains two-thirds its weight of oxygen. Gay Luftac 

 and Thenard, from treating boron with nitric acid, make 

 it to contain one-third its weight of oxygen ; but this refult 

 ii not to be relied upon, fince boracic acid is volatile both 

 with water and the nitric acid. 



Sir Humphrey Davy found that 90 parts of potafti were 

 required to neutrahze 160 of boracic acid. This will give 

 80 for the weight of the atom of boracic acid, potafti 

 being 45', and hydrogen I. If, according to fir Humphrey, 

 it contains two-thirds of oxygen, then the atom of boron 

 will be 27. 



Dr. Thomfon, from the experiments of Berzelius, which 

 are in fome meafure corroborated by thofe of fir Humphrey 

 Davy, makes the atom of boron 5.5, hydrogen being i. 

 This is the weight of the atom of carbon, to which boron 

 feems in other refpeAs allied. If, like carbon, it combines 

 with two atoms of oxygen, then boracic acid will be 



^5 



