SPECIFIC GRAVITY NOMENCLATURE. 29 



express precisely the weight ofan equal bulk of water,) and then divide 

 the first weight by this last, and the quotient will be the specific gravity. 

 This rule is founded on the hydrostatic law that when a solid is immers- 

 ed in a fluid, it loses a portion of its weight exactly equal to the weight of 

 the portion of fluid displaced ; that is, equivalent to the weight of its 

 own bulk of that fluid. If the solid be lighter than water, as in the 

 case of cork, its specific gravity may be found by suspending a small 

 glass funnel from a scale beam, and counterpoised so as to be just 

 below the surface of the water ; the lighter body is then to be thrown 

 up under the funnel, which will, of course, destroy the equilibrium, 

 and elevate the funnel. Ascertain how much weight will counteract 

 the buoyancy of the light body, add this to its weight, and divide its 

 weight by the sum ; the quotient must, of course, be less than unity. 

 To ascertain the specific gravity of gases, it is only requisite to 

 fill a globe of known capacity with the gas, then to weigh it, and to 

 divide the result by the weight of the same bulk of atmospheric air, 

 which is the standard, or unity, for gases. It must also be remem- 

 bered that the specific gravity of gases is influenced by i\ie\Y purity, 

 their hygrometric condition, the degree of pressure to which they 

 are subjected, (their bulk being inversely as the pressure,) — and 

 their temperature. 



Chemical nomenclature. — In the formation of a chemical nomen- 

 clature, the names given to many of the elements were expressive 

 of some of their striking properties : — thus oxygen, from two Greek 

 words, signifying to produce an acid, from the idea that oxygen was 

 the sole acidifying principle ; hydrogen, from two words signifying 

 to produce water ; — others again derived their names from words 

 expressive of their colour, as chlorine, iodine, cyanogen, &c. The 

 compounds of oxygen were named oxides or acids, according as 

 they do, or do not possess acidity. Acids derive their name from 

 the substance acidified by the oxygen, by the termination in ic ; 

 thus sulphuric, carbon^c, phosphorzc, &;c. Should the substance be 

 capable of forming more than one acid, the name of that containing 

 least oxygen is made to terminate in ous, as sulphurizes, riiUovs, 

 &c. When the same substance forms several acids with oxy- 

 gen, the Greek preposition hijpo is generally prefixed to express 

 the relative quantity of oxygen ; thus, A^/ponitrous and hypo^xA- 

 phuric indicate acids containing less oxygen than nitrous and sul- 

 phuric acids respectively ; sometimes the particle per is prefixed to 

 express the highest amount of oxygen, as perchloric acid. 



The nomenclature of the salts is made to depend on the termina- 

 tion of their acid ; thus, acids ending in- ous form salts terminating 

 in ite, as sulphiYe, mixite, from sulphurizes and m\xous acids ; acids 

 ending in ic, as sulphuric or nitr^c, form salts terminating in ate, as 

 sulphate and liiXxate, 



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