M18TRY. 



10 K> delicate, that one part in 60,000 mar be readily 

 detected, of MIT substance with which the tost affords a 

 colour or precipitate Indeed, extrouio danger may 

 cnmuo from neglect of this. For instance, were a tl r 

 chloride of nitrogen to be placed on a greasy or oily 

 duh, it would instantly explode, and break the vessel 

 into fragment*. Neatness aud care should be observed 

 in all experiment*. This will induce a general habit, 

 which will be of value to the itu.l.-ut in every pursuit 

 he takes in hand ; and without them a person cau never 

 uoomxt in chemical science. 



Beginners are often tempted to use large quantities 

 of chemical*, where experienced persons would omploy 

 but a small portion. This ormr often produces an 

 exactly opposite effect to that intruded. Thus, if a 

 mail i|ii.intity of iodide of potassium be added to a 

 solution of bichloride of mercury, a yellow precipitate 

 will be produced ; a still larger quantity will afford a red 

 precipitate ; and one in excess will redissolve all the , 

 pitate, and leave a transparent and colourless solution. 



Heat should be applied gradually to all glass vessels, 

 lest they should be fractured. A sand-bath is some- 

 times employed between the vessel and the source of 

 heat An iron or copper basin containing sand, answers 

 well for this purpose, by allowing the heat to pass gra- 

 dually, and so avoiding the risk which would bo run by 

 applying the flame directly. As we proceed, we shall 

 suggest other precautions when needed, aud thus endea- 

 vour, as far as possible, to ensure the successful per- 

 formance of all the experiments we shall introduce 

 illustrative of our subject. 



CHEMICAL TERMS AND SYMBOLS. 



BEFORB entering on a description of the natural history 

 of the elements and their compounds, we shall make a 

 few remarks in reference to terms employed to designate 

 various substances; and the symbols, the use of which 

 tends to materially assist the student in his progress, 

 and saves much time and space. 



In the early days of chemical science, every one "did 

 that which was right in his own eyes," when naming 

 newly-discovered substances. Hence arose such terms 

 as "Glauber's" and "Epsom salts," "cream of tartar," 

 "a>]ua regia," and the like. In fact, the names then 

 adopted, just illustrated the mental character of their 

 invriitors, who, at all times, leaned more to their ima- 

 gination than to their reasoning powers for a guide. As 

 the number of compounds increased, or became known 

 with respect to their constitution, great inconvenience 

 was felt, and the necessity of some system of uomeucla- 

 turu was recognised. 



Without rut. 'ling into historical details on this sub- 

 ject, we state that the present plan has the advantage 

 over all others whicli have been proposed, by giving an 

 inxight into the composition of the object designated. 

 This we shall perceive as we proceed, and the student 

 will soon appreciate its value. In naming elementary 

 bodies, the old plan is still maintained to some extent ; 

 but thin is of slight consequence, because each has but 

 little relation to the others, and, therefore, a distinctive 

 i advantageous, no matter whence its source. 

 i, however, we speak of bodies compounded of ele- 

 *, it is desirable that wo should know of what they 

 are composed. We will take, for instance, the classes of 

 < called oxides, A-c., acids, and salts. The term 

 is applied to any substance containing a n 

 united with such a prop' tvgen as is not suffi- 



cient to make it an and in ita pro]>ertie8. Thus, the 

 rust of iron, commonly so called, is termed oxide of iron 

 in chemical language. If it have but one equivalent of 

 oxygen to one of metal, it is termed the protoxide ; if 

 two of oxygen, the Mnooide ; and so on Greek prefixes 

 being used to indicate the relative proportions existing 

 between the metal and the oxygon. 



urinations of metals and chlorine are called 

 rid**. Thus, common nail, which contains e|,|..nnc and 

 tho metal sodium, is termed chloride of totlium. r 

 Libations of iodine, bromine, and fluorine, are similarly 



termed iodide*, bromide*, and ftiwridm. l',y this ar- 

 rangement we at once i>erceivo the nature of tho com- 

 1 from its title. Wo may proceed a step further 

 with respect to acids. Generally 



indicate their origin; thus, Kiilplin in. .1 



from sulphur, by its ooniliinaiion with oxygon; nitric 

 from nitre; hydrochloric acid from chlorine and 

 hydrogen; but still the system to which wo have re- 

 ferred, is not so strii i out with many of those 

 compounds, as is shown in the i:..iu. oxalic arid, acetic 

 acid, etc. When, however, we deal with salts, we find no 

 exception to the rule ; and we here must explain what we 

 ni.-an by that term. A salt is always composed of an 

 acid ami a base. Thus, in car 1 ). >nato of soda, wo have 

 the nfi<l as tho carbonic, and the Ixtse is the soda. In 

 all the salts, both base and acid are indicated. In 

 this application of the present system of nomenclature, 

 wo liud tho greatest convenience; as the following in- 

 stances will show, when we compare the new with tho 

 old names. Thus, "copperas" is now called sulphate of 

 iron, because it contains sulphuric acid and iron ; 

 "white vitriol" is the sulphate of zinc; "Glauber's 

 salts," sulphate of soda; "Epsom salts," sulphate of 

 icsia; "blue vitriol," sulphate of copper. Combi- 

 nations of nitric acid with a base, are similarly named. 

 Thus, nitre is called nitrate of potass ; and so each salt 

 bears its own character in its name. 



There are other combinations which differ from acids, 

 'i which we must also direct attention. Thus, tho 

 combinations of sulphur with metals are trrmrd sul- 

 phides ; of phosphorus, phosphides ; of carbon, carbides. 

 In earlier chemical works, the terms sulphuret, phos- 

 phuret, and carburet, were used; but these have been 

 changed, because of the analogy existing betu 

 substances and the cldorides, <tc. Other terms ana- 

 logous to these will be met with when we study tho 

 chemistry of organic bodies ; but such will bo duly 

 noticed in thoir proper place. 



When the proportion between acid and base varies, 

 their prefixes are employed to signify the fact. Thus, 

 we have proto-sulphate of iron, containing one equivalent 

 of acid to one of metal U-carbonate' of soda, contain- 

 ing two equivalents of acid to one of base; anil thus, 

 not only are the names of the constituents afforded, but 

 their relative proportions are also indicated. 



These instances will be sufficient to introduce our 

 readers to the principles of chemical names ; and we 

 shall now proceed to refer to symbols, by which 

 oxides, acids, salts, <tc., are distinguished. It is de- 

 sirable that the student should acquaint himself with 

 that of each element, as it will much facilitate his pro- 

 gress. A table of symbols will be found prefixed to the 

 next chapter, in which wo shall commence the descrip- 

 tion of each element and its compounds. 



Generally gpe ii element is distinguished by 



the initial letters of its name. Sometimes those of the 

 Latin term are used in preference to the English. The 

 following are examples of each : 



Hydrogen has the symbol of ... H 



Oxygon O 



Sulphur S 



Iron Ferrum Fe 



Tin Stammia Su 



Silver Argentum Ag 



By such ari arrangement, each element, having a 



'to symbol, is readily distin^uishis! from all others. 



When compounds are designated, then the symbols of 



Mstitnonts are used together, thus 

 HO, hydrogen and oxygen, represent water. 

 Ag O, silver and oxygen oxide of silver. 



Ag Cl, silver and chlorine ,, chloride of silver. 



If, however, there are more than one equivalent of 

 either el. 1,1, -nt. tle-n such is shown by means of small 

 figures; as -S O 3 , sulphuric acid, which, when frou 

 from water, is a compound of one equivalent of sulphur 

 to throe of oxy-.: 



Occasionally, a combination of symbol:-, is required; 

 and, in that case, the symbols of c-aeh compound are 

 arranged together, by means of which tho entire con- 



