EXPLAI^^ATOET NOTES. 



Each of the following tables, with two exceptions, is divided into five columns. 

 The first contains the Name of the Substance, the second its Formula, the third 

 its Specific Gravity, the fourth its Boiling Point, and the fifth its Melting Point. 

 From the Table of Elementary Substances, however, the column for formula 

 is omitted ; and in the Table of Alloys, no boiling points are given. The au- 

 thorities are added as foot-notes to each page. 



Some abbreviations are necessarily used. In the first column, the letter "s." 

 placed after the name of any substance, shows that that substance is a solid, 

 or was examined in the solid state. The letter "1." similarly used, stands for 

 liquid. Thus, " Acetic acid, s.," stands for solid acetic acid ; and " Chlorine. 1.," 

 for liqupfied chlorine. 



Among organic substances, the abbreviations " iso," and the Greek letters 

 alpha or beta are sometimes appended to the name of a substance. These 

 are simply to distinguish isomers from each other; as, for instance, isopropyl 

 from propyl compounds, and alpha- from beta-xylidine. 



In the Specific Gravity column the letters "s." and "1." are also employed, 

 and indicate that the determinations to which they are appended are for the 

 substances in question in the solid or liquid state. The letter "a." attached to 

 a determination shows the latter to be merely approximate. Expressions like 

 "m. of 3," "m. of 5," &c., affixed to a number, show it to be a mean of 3, mean 

 of 5, &c., determinations. And the abbreviations "Precip.," "Artif," "Cryst.," 

 "Ign.," &c., stand simply for the words precipitated, artificial, crystallized, 

 and ignited, and express of course the character of the material employed in 

 making a determination. 



In the column devoted to Boiling Points, the letter "a." is again used to 

 express approximation. Thus, "160° a." stands for aboid 160° When baro- 

 metric measurements are given, "m.m." of course stands for millimetres. 



The phis and minus signs are employed to show that a determination is a 

 lU 



