432 Mr. Prideaux's Continuation of the Table of AtomicWeights. 



Acids are on the column next the slider to the right; cry- 

 stallized and hydrated acids in the succeeding column ; and 

 chlorides in the two columns furthest right. Multiples of 

 oxygen, 1 to 12, are in the second column; of hydrogen, 10 

 to 50, and carbon, 2 to 10, in the third ; and of nitrogen, 

 1 to 5, and water, 1 to 25, in the outer one. 



Iodides and bromides, being heavy, are all near the foot, 

 on their respective sides ; and therefore easily found, without 

 crowding the other substances, by confining them to particu- 

 lar columns. 



In linking from column to column, where it could be done, 

 to prevent the embarrassment of needless multiplication of 

 lines, precision has been allowed to give way in a few un- 

 important cases ; but the deviation has rarely amounted to 

 an hundredth part, particularly on the scale of salts. 



The salts not packing so close as the binary compounds, 

 and hence requiring a slider with longer degrees, an adjust- 

 ing line ») tJk is drawn across the face on each side, to 



set the two scales in accordance. Thus, when a salt and a 

 chloride are to be used together"; when the binary or ele- 

 mentary ingredients of a precipitate are to be ascertained ; 

 or, in short, whenever the relations between salts and binary 

 compounds or simple bodies are to be examined, — each slider 



must be set with the same number against the line xJ> ^JT, 



and they correspond throughout. 



As a general table of equivalents, set 1 "0 against O (oxy- 

 gen), and the numbers are on the oxygen scale; then move 

 the slider and bring *8 against O, and the numbers are on 

 the hydrogen scale, disregarding the decimal point. In the 

 latter case the scale of salts must have its numbers corre- 

 spondingly decupled. 



The advantage alluded to in the outset of this notice, as 

 belonging to the analytical character of these symbols, in 

 cases of compound salts, may be thus illustrated. Suppose 

 we have to prepare acetate .of alumina from alum and acetate 

 of lead: the symbol shows that alum contains four atoms 

 of sulphuric acid ; acetate of lead but one atom of oxide ; 

 and hence that four atoms of the latter salt are requisite for 

 throwing down the acid; and that three atoms of acetate of 

 ammonia will remain in the solution. So if we use cream of 

 tartar, red sulphate of iron, dichloride of lime, &c. we are 

 guided at once by the symbol what proportions to employ, 

 accordingly as the acid or base be the subject of operation. 

 A similar convenience is afforded in looking out the quanti- 

 tative ingredients of a compound salt. 



These advantages are only in promptitude; for a knowledge 



of 



