BAUIUM STROXTICU.] 



CHEMISTRY. 



391 



Neither magnesia nor its salts have any application to 

 the arts or manufactures ; and their uses are almost 

 entirely confined to medicinal purposes. 



BARIUM. 



THIS metal is obtained by the action of potassium on 

 baryta, its oxide, and presents a similar appearance to 

 those obtained from other earths. Its symbol is Ba, and 

 the equivalent equals 08 '5. 



Baryta derives its name from its great specific gravity, 

 being the heaviest of the earths. It is the protoxide of 

 the metal, and may be obtained by heating the carbonate 

 to redness, when a grayish-white powder is produced, 

 much resembling lime in its leading properties. In the 

 state of a hydrate, baryta may be crystallised ; it has an 

 alkaline reaction on test-papers, and is highly poisonous. 



The sulphate of baryta, or heavy spar, is found in 

 many places. It may be prepared artificially, by adding 

 sulphuric acid or a sulphate to any soluble salt of baryta ; 

 ami the affinity between the base and acid is such, that 

 baryta can separate sulphuric acid from any of its salts 

 in solution. Baryta salts are, in fact, the usual tests 

 employed in the laboratory for the presence of that acid. 

 The nitrate is easily obtained by dissolving the native 

 carbonate in nitric acid ; and it is used as a reagent. 

 If dissolved in alcohol, it gives a rich green flame on 

 ion of the spirit. It is largely employed by fire- 

 work-makers as an ingredient in green fire. The chlo* 

 which is also a useful test, is readily produced by 

 the solution of the carbonate in hydrochloric acid, from 

 which the salt, in a crystallised state, is readily obtained. 



A peroxitlb of baryta is an interesting compound, from 

 the fact that it enables us to procure a peroxide of 

 hydrogen. It is produced by heating caustic baryta 

 in oxygen gas, at a temperature a little short of a red 

 heat 



STRONTHM. 



Tins metal, like barium, is, at present, only obtainable 

 in minute quantities, either by voltaic action as an 

 amalgam, or by the action of heat and potassium on 

 strontia. It has similar properties to barium ; its 

 equivalent is 43 '8, and the symbol, Sr. 



Strontia is obtained by heating the carbonate, which 

 is a somewhat abundant mineral, found at Strontian, in 

 Scotland. It has an alkaline action on test-papers, and 

 is soluble in water, from which it may be obtained as a 

 crystalline hydrate. Native sulphate of strontia is 

 termed celestine, and is found in some of the northern 

 counties of Bnguod and Scotland in a crystalline state, 

 some of the specimens presenting a beautiful appear- 

 ance. The nitrate is produced by dissolving the car- 

 Ixmato in nitric acid. This salt affords a fine deep-red 

 flame when burned with spirits of wine, and is used in 

 the manufacture of fireworks to produce coloured fire, 

 <fec. , which affords a splendid deep- red colour. The car- 

 bonate, as we have remarked, is found in a natural state. 

 It may be produced artificially, for laboratory uses, by 

 exposing the hydrate to the action of carbonic acid. 

 The chloride and other salts are producible by means 

 similar to those for making barytic salts. 



It only remains for us to mention, that there are four 

 earths very rarely met with, whicli complete the list of 

 that class of bodies. They are Thoriua, Yttria, Glucina, 

 and Zirconia. Thoriua is obtained from the mineral 

 called Thorite. Yttria from Gadolonite, <fec. Zircouia 

 from Zircons ; and Glucina from a few minerals, amongst 

 which the emerald is the chief. The properties of these 

 earths generally agree with those of alumina or other 

 earths already described ; but as they have been scarcely 

 investigated, any description of their individual pro- 

 perties is almost impossible. They respectively afford 

 metallic bases analogous to those of earths generally. 



TESTS FOR METALS, ETC. 

 Is our previous pages we have described the leading 



properties of metals proper, alkaline, and earth-pro- 

 ducing metals ; and we shall presume that our readers 

 have become well acquainted with their individual cha- 

 racteristics. We shall now proceed to mention the 

 usual mode of detecting the presence of the leading 

 metals and their compounds. This will serve the double 

 purpose of teaching the art of testing and of giving 

 exercises, by means of which the student may become 

 practically acquainted with the various states and con- ! 

 ditions in which metals and their oxides are met with 

 in nature, or in the course of laboratory practice. We 

 shall resume the plan of experiments, and point out the 

 various tests, and the mode of using them in the 

 manner adopted by analytical chemists. Our readers, 

 by trying the following experiments, will thus obtain 

 an insight into the methods of inorganic ai.J organic 

 analysis, on which we shall have to dilate hereafter. 



The object of a test is to discover, by the addition of 

 one body to another, the presence of that which is being 

 sought for; and our article on Arsenic illustrates one 

 application of this fact. To apply the proper test in 

 any case requires that we should be fully acquainted , 

 with the properties of the test, and also of the substance ' 

 tested ; and nearly every substance so employed has 

 already be.-n fully described. If our readers, therefore, 

 have any difficulty in this respect, they need only refer 

 to the substances named under the heads of the re- 

 spective metals, whea they will at once obtain the re- 

 quired information. 



The state of solution, if not always necessary, is, at all 

 events, the most convenient for the purposes of testing. 

 The particles of a body are then in the most favourable 

 condition to obey the laws of chemical affinity. Being 

 suspended in a fluid, they are easily moved ; and so, 

 whether remaining in solution or precipitated as a 

 powder, they are at once under our command. For the 

 following experiments a number of test-tubes, Florence 

 flasks, some filtering paper, a funnel, stirrers, <fec., are 

 required. We may also notice, that in many cases slips 

 <>( window-glass, or white plates, will answer every 

 purpose ; for on either of these the peculiar and distinc- 

 tive colour, <tc. , produced by a test, are readily observed. 

 To assist our readers, we shall give a list of a few 

 tests wliich will be needed ; and shall also refer to the 

 iii which they have already been mentioned. With 

 the exception of the acids, all the tests should be dis- 

 1 in distilled water, and kept in glass-stoppered 

 bottles. Besides the sulphuric, nitric, and hydrochloric 

 acids, the following are the chief tests : 



Hydro-sulphuric acid .... See p. 370. 



Hydro-sulphate of ammonia . . 370. 



Caustic potass ,, :>,Sli. 



Carbonate of potass .... ,, 



Prussiate ., ,, ,, 378. 



Caustic soda ,, 



Carbonate of soda , , 387. 



Chloride of sodium ,, 387. 



Sulphate of iron ,, 377. 



Liquid ammonia . . . . . ,, 324. 



Carbonate of ammonia .... 324. 



Chloride of barium 391. 



Nitrate of baryta 3!U. 



silver 374. 



Sulphate of soda ,, 387. 



Chloride of platina ,, 372. 



Chromate of potass ..... , , 384. 



Nitrate of cobalt ,, 384. 



Iodide of potassium , 386. 



Besides the above, a few slips of copper, zinc, and iron, 

 and some litmus and turmeric paper should be provided. 

 \Vi: shall now show how the,e tests are employed ; 

 first giving some introductory experiment! to initiate 

 our readers, before we proceed to give separate tests for 

 each metal. 



Experiment 68. Dissolve a crystal of the proto-sul- 

 phate of iron in distilled water ; and divide the solution 

 into three test tubes. Into one pour a few drops of a 

 solution of the prussiate of potass ; a blue precipitate 

 will be produced. 



