278 



On Chemical Tests. 



[Oct. 



of platinum, if a yellow precipitate takes place, the base is potash: if 



no precipitate oc -urs, the base is soda. 



XLVII. THS FOBEGOING EXAMINATIONS HAVING DISPOSED OF THE BASES, 

 AND METALS, I CLODED IN THE LIST BEFOKE ENUMERATED, THE FOLLOW- 

 ING EXPERIMENTS ARE 



TO DISCOVER THE ACID, OR NON-METALLIC BODY. 



xlviii. r. To the substance dissolved in water, or pounded and mixed 

 with a little water, add muriatic acid; if effervescence occurs, accom- 

 panied with the well known odour of sulphuretted hydrogen gas, it in- 

 dicates the presence of a sulphuret : but if the gas is in-odorous, it 

 indicates carbonic acid in combination with some of the foregoing bases. 



xlix. To ascertain whether both carbonic acid and sulphur are present, 

 provide a vial with a small glass tube bent twice at right angles. Place 

 a portion of the pulverized substance in a vial and pour upon it dilute 

 acid : place one leg of the tube in the vial and allow the gas to pass 

 through the tube into another vial containing a solution of muriate of 

 barytes, or lime water, to either of which a little ammonia has been add- 

 ed; let the other leg of ihe tube dip below the liquid in this second 

 vial, and close both vials.* If a white precipitate takes place, which 

 dissolves with effervescence in dilute acid, the substance contains car- 

 bonic acid. The sulphur wiil be recognized by the smell of sulphuretted 

 hydrogen. 



l. 6'. If muriatic acid produces no effervescence add to a neutral so- 



„ , , . , , . lution of the .substance, muriate of barytes, 



Sulphuric, phosphoric, * 

 Arsenic, boracic, fluoric. and if a vvhite precipitate takes place the 



presence of one of the acids in the margin is indicated. To ascertain 



which, proceed as follows: 



li. Add muriatic acid to the precipitate ; if it remain unaltered, the 



acid is sulphuric : but if it dissolves, the following experiments must 



be made. 



Lti. Reduce a portion of the substance under examination to powder, 

 and add thereto concentrated sulphuric acid, either in a leaden or a pla- 

 tina dish ; prepare a piece of glass coaled with wax, and trace any figure 

 through the wax reaching to the glass. Warm the mixture gently, 

 cover it with the glass, and if the glass after some time becomes cor- 

 roded where the tracings were made, the substance proves to he a fluo- 

 ride, i. e. containing fluoric acid. 



Mil. If this effect does not occur, put a portion of the pulverized sub- 

 stance into a porcelain or platina capsule, and add a few drops of sul- 



* It is necessary that the muriate of barytes, or lime water should be shielded from 

 the atmosphere. 



