: 



CIIKMISTKV. 



[or AUIATIVK AN 



lime, will also, roort likely, contain a small portion of 

 in .11 ; hone* another step u ueoowary to duUxt the oxide 

 of tJmt mrll 



I'.i a mall quantity of the solution a, add a few 

 drop* of nitric acid, and 'heat it. TI..-M pour in a few 



a M-'M!I. : ite of potass, when, if iron 



be proseut, a bin. will at once be produced. 



.iy now c- qualitative analysis of the 



marble to have been completed and verified ; and to 

 make oar progrew more easy, we ahall recapitulate each 



) \\ | -:il tin- solubility of the marble in water. 



2. In a we effected a solution in hydrochloric acid. 



3. In fc we obtained a precipitate by means of ant- 



acid. 



4. In f we showed that only tho sulphates of stroutia 

 or lime could have Uvn produced. 



6. In d we found that tho precipitate could bo sul- 

 phate of lime only. 



6. By the process named in e we proved the presence 

 of carbonic acid. 



7. Y\V \. !:;.-! .mr previous discoveries by heating the 

 substance as in /. 



R. And, lastly, anticipating the presence of iron, we 

 tested for Us oxide, and obtained a precipitate of Prus- 

 sian blue in g. 



We have thus succeeded in obtaining, separately, each 

 of the constituents of the marble by way of analysis. 

 Each step, it will be observed, depends on that taken 

 previously ; and from this easy example, the student 

 may learn the general method of conducting tho quali- 

 tative analysis of many substances. 



In carrying out this initiatory experiment, we h.-ive 

 chosen a substance which is so simple in its constit 

 as to leave no doubt of accurate results, because every 

 { specimen of marble and chalk has, as near as possible, 

 an identical i :. We must, however, inform 



the student, that baryta, strontia, liuie, and m >-!,;:,. 

 present, as near as can be, tho same appearance when 

 tested in solution by some reagents. For instance, the 

 earbonate of the alkalies would precipitate the carbonate 

 of each of these earths as a white powder. Tho same 

 may be said of oxalic acid and oxalate of ammonia. 

 ; had Mich tests only been 1, the student 



would scarcely have advanced a step, because the indica- 

 tions produced would liavu Wen undistinguishable. By 

 the plan, however, which wo have described, each s 



ror was successively eliminated, and so the true 

 composition of the marble wan at last arrived at. The 

 progress in chemical analysis, when properly conducted, is 

 just as logical as a problem in geometry or an equation 

 in algebra. The value of line* or quantities is gradually 

 estimated in those sciences from data ; and similarly in 

 chemistry, we obtain, in a physical form, analogous 

 results. 



Wo must next examine more difficult instances ; and 

 by suggesting mixtures of various stilwtan . shall 

 indicate the means to ba employed in detecting their 

 constituents. 



l-triment 83. We shall now proceed to analyse a 

 piece of clay, which, generally *]>eaking, contains four 

 or more sulmtouces. Our attention, however, will l>o 

 confined to the detection of the silica, alumina, limo, 

 and iron ; and the following plan may be adopted. 



(a.) Take a small piece of the brown-coloured clay, 

 such as U used in brickmaking, and heat it for some 

 time in a ladle, but no; r ! hot, for tho pnrjK>so of 

 driving off water in a free state, and to break up thu 

 crystals of sulphate of lime which may be pi 

 Transfer the mass HO obtained to a glass flask ; add 

 abundance of di tilled water, and agitato the contents of 

 the vessel fur some time. This will dissolve out a por- 



of sulphate of lime, which is more soluble ii 

 than in hot water. Let the whole stanil fur some time, 

 and then pour off the clear liquid into another vessel. 

 Evaporate a portion of the liquid to dryness in an 

 evaporating dish ; if a powder lie obtained which in ) 

 soluble in much watr, it may be assumed as milpluito of 

 lime, but may also be tested as in Experiment B2. 



('.) A brown coloured mass will be 1. ft in the flask, 

 which ih insoluble in water. To this add dib 

 chloric acid, and boil for some time t e all 



soluble matter out. By this the carbonate of lime, 

 alumina, and iron, will )> L The clear liquid is 



accordingly to be poured oil' into another vessel. 

 in. ire hydrochloric acid added to the powder in the tlask. 

 The contents are to be boiled, and when cool, are to be 

 added to the previous .solution. The remaining mass is 

 to be washed with distilled water, ami thu wa 

 also to be added to tho solution already efi.< ted. Jty 

 these means, all matter soluble in dilute hydrochloric 

 acid will have been removed, and little else but 

 w hi.-h is insoluble, will remain. Of this we shall speak 

 hereafter. 



i The solution from '< will contain lime, alumina, 

 and iron ; and eaeh of these is to bo tested for 

 ratcly. \\eiv we to add alkalies, or an alkaline . 

 nate, we should obtain an abundant precipitate of all tho 

 bodies iu solution ; and this would only perplex us, and 

 compel a re-solution of some of them. Our o 

 however, may bo readily attained by first removing tho 

 limo as sulphate; secondly, the alumina; and, 1 

 the iron may In- .Now, 



as alumina and iron are both soluble iu sulphuric 

 and lime produces an almost insoluble precipitate with 

 it, we add dilute sulphuric acid to the solution, and so 

 obtain the sulphate of limo. By this we get rid of one 

 of the three constituents of the clay namely, the car- 

 bonate of lime ; the existing sulphate having air 

 been disposed of. 



(/.) The solution freed from the salts of lime most 

 likely to be present, now contains alumina and oxide of 

 iron ; and after adding a little nitric acid, bc.il for a 

 short time in a fla.sk ; then divide the liquid into two 

 portions. To one add prussiate of potass, when the iron 

 will fall down as a blue precipitate. The presence of 

 iron is thus evid. 



(e.) To the remaining portion of the solution in <!, 

 add a dilute solution of potass. ' A precipitate will at 

 once bo afforded of alumina : allow it to settle, and 

 then add an exccu of a solution of potass, and heat it. 

 The alumina will be completely dissolved. To this 

 add a solution of sal-ammoniac, when tho alumina 

 will be again thrown down. The alumina present in 

 the clay is thus detected. 



\\'n have thus discovered that clay consists of 

 alumina, lime, and oxide of iron ; but have yet to 

 examine the insoluble matter left in process b, after 

 :ing with hydrochloric acid. This leads us to 

 another branch of analysis namely, that in which 

 matter containing silica is to be examined. The follow- 

 ing course must be adopted. 



(/.) As silk-ions matter is insoluble in all liquids 

 except hydrofluoric acid,* wo must bring it into a 

 soluble state by means of a flux. The mass left in h 

 is therefore to lie removed, washed, and dried, and then 

 to be mixed in the mortar with three or four times its 

 weight of carbonate of soda, or potass. It is then to be 

 transferred to a Berlin porcelain or English crucible ; 

 and heat for two hours at a full ivd heat. A gas-furnaco 

 may lie employed if a Berlin crucible' be used ; or a 

 common coke tire will answer equally as well, if common 

 crucibles are adopted. Tho sand and alkali will unite, 

 and form a silicate, which is easily soluble in water. As 

 soon as the entire mass is completely fused, the crucible 

 is to be removed from the lire, ami allowed to . 

 The whole may then be placed in a large evaporating 

 dish, and dilute hydrochloric acid is to be poured iu to 

 the crucible; 01 maybe broken out, and 



put into the evaporating dUh alone, as a little loss is no 

 ithe anahsM of this kind. 



(;/.) I ';.. i. ultin;,' mixture from tho last process is to 

 be oautioi, . and when the di-h 



i< <|iiite cool, dilute hydrochloric acid is t.. i in. 



This will dissolve out all but the silica, which will bo 

 . a gritty white powder. It is thus also removed 

 from the clay. 



Dec anlf, p. 3S9. 



