110 



CHEMISTRY. 



[Lesson VI 



contains one atom, the silica two atoms, 

 and the sulphuric acid three atoms, of 

 oxygen. When a compound contains 

 proximate and ultimate elements, the mode 

 of union is expressed by means of points, 

 commas, -f- signs, and brackets. For 

 example, crystallized sulphate of ammonia 

 (one atom of ammonia, one atom of 

 sulphuric acid, and two atoms of water) 

 is Nil 3 + SO" + 2 HO = NH 3 SO 3 , 

 2 HO N s"II. The dots under the 

 symbol of a body denote atoms of hydrogen ; 

 and commas, or strokes leaning from right 

 to left, atoms of sulphur as, when we 

 express the tersulphuret of molybdenum, 



thus, Mo. A number placed on the right 

 and upper part of a symbol, expresses the 

 number of atoms of the substance denoted 

 by the symbol thus, SO 3 means one 

 atom of sulphur, and three atoms of oxygen. 



59. T. Why do you place the number 

 above the symbol, instead of below, which 

 is more usual with chemists ? 



P. Because it is more easily read than 

 when placed below. 



60. r. What do the numbers placed 

 before symbols mean ? 



P. A number placed before several 

 symbols multiplies them all as far as the 

 next -f- sign, or comma ; or, if the number 

 is placed before a bracket, it multiplies all 

 the numbers or symbols within the brackets 

 thus, KO + 2 CO 2 + HO = KO, 

 CO-, HO = xc 2 ill means, that one 

 atom of potash, two atoms of carbonic acid, 

 and one atom of water, unite to form 

 bicarbonate of potash, and 8 (CaO, ScO 3 ) 

 + KO 1 , 2 S, iQ* + 16 Aq., gives the 

 composition of apophyllite ; 2 HO means 



two atoms of hydrogen, and two atoms of 

 oxygen. 



(il. T. What is meant by a stroke over 

 a symbol ? 



P. Berzelius used it to express the 

 vegetable and animal acids thus, T, sig- 

 uiiies tartaric acid, and P formic acid. 



62. T. Why have some symbols a 

 stroke under them ? 



P. It is an abbreviation sometimes 

 used to denote two equivalents of a sub- 

 stance ; thus, Fe instead of Fe a O 3 , or it 

 may be written -F e O 3 . 



63. T. Have not certain compounds 

 particular symbols appropriated to them ? 



P. Yes; water is written Aq ; cyano- 

 gen, Cy ; tartaric acid, T; + citric acid, c; 

 acetic acid, A ; Morphia, M ; &c. 



6-1. T. How is the water of crystalliza- 

 tion expressed ? 



P. By attaching an li to the symbol of 

 the substance ; thus Ah denotes the hydrate 

 of acetic acid. 



GENERAL QUESTIONS ON LESSON V. 



1. How is it that certain substances, 

 composed of the same materials, possess 

 different qualities and forms ? 



2. Explain the meaning of isomeric, 

 and give its derivation. 



3. How do we know that atoms have 

 weight ? 



4. How are the elementary bodies ar- 

 ranged and expressed ? 



5. Do symbols express the elementary 

 bodies in a satisfactory manner >. 



6. Give illustrations of the various 

 symbols. 



LESSON VI. 



WE have found how certain substances may be expressed by abbreviating them, and 

 as every beginner in chemistry is somewhat alarmed by seeing so many great h's, o's, 

 and other letters, combined with -f's and figures staring him in the face, we must take 

 this opportunity of recommending that the symbols which are, in fact, the alphabet of 

 chemistry be practised by the pupil with a piece of soft chalk on a slate or board. If 

 a little attention is given to the subject, an hour's practice will overcome the difficulty. 

 It is said that chemistry has a great many hard names, but, really, it does not abound 

 with more than any other science, and after all, they are very simple. Tor example, 



