116 CHEMISTRY. [Lesson VIII 



forget the improvements made in the manufacture and colouring of glass, the discovery 

 of gun-cotton; the separation of wolfrum from tin, by Mr. Oxland's process of roasting; 

 electro-gilding and silvering, the electric telegraph, the Bude light, porcelain manu- 

 facture; and the preservation of wood, canvass, &c., by Sir W. Burnett's chloride of 

 zinc ; they furnish us with admirable examples of the application of Chemistry to 

 useful purposes, benefitting mankind by its results, and turning our thoughts to Him 

 who developes the faculties of invention. 



Before commencing the investigation of the elementary bodies, we must notice some 

 of the apparatus and processes required. Rectification is performed by the aid of heat, 

 and is only the repeated distillation of any product obtained by distillation, but as it 

 requires a lower temperature than distillation, the more volatile parts only are raised 

 and pass into the receiver, while the impurities remain behind. According to the 

 process and the results, so it has received its name ; thus, when the liquid is distilled 

 from any substance it is called abstraction ; when the product is re-distilled from the 

 same materials, or another supply of the same materials, it receives the name of 

 cohobation; and when the object is to increase the strength of the fluid by leaving the 

 watery part behind, as in the case of spirits, the process is called concentration or 

 dephlegmation. Sublimation is another process required to be performed ; the product is 

 called a sublimate. It consists in driving off certain volatile parts of substances, and 

 condensing them again in a solid form, which is done by employing a common crucible 

 with a cone of paper over it in some cases ; in others, two flasks placed mouth to 

 mouth may be used. 



In determining the weight of bodies, the Apothecaries or Troy weight is commonly 

 used, according to the following table : 



POUND [libra lb.] OUNCES [uncia |] DRACHMS [drachma 5] 

 1 == 12 = 96 



1 = 8 



1 



SCRUPLES \scrupulus 3] GRAINS [granum, gr.] 



288 = 5,760 



24 = 480 



3 == 60 



1 20 



And a common Apothecary's balance with the necessary weights, is all that is required. 

 Liquids are measured by the following table, in which it will be seen that drops are 

 not recognised, as they are very liable to vary in quantity from various causes. 

 Graduated glass measures of different sizes are used for measuring : 



GALLON [congius C] PINTS [octarius 0] FLUID OUNCES [flu id- un 



1 = 16 



1 



FLUID DRACHMS [fluid drachma /5] MINIMS [minimum 



1,024 61,440 



128 = 7,680 



8 = 480 



1 60 



The Latin names for the various weights and measures, and their distinguishing signs, are inserted 

 between bracket*. The Latin names are given in the singular. 



