194 CHEMICAL TECHNOLOGY. 



those arts of a chemieal nature, which more immediately flow from 

 any one branch of manufactures, especially when we consider that such 

 collateral arts are often necessary to the economy of a particular branch 

 of manufacture. 



Emanating from chemistry, chemical technology has been 

 usually treated as a branch of that science, and has been correctly 

 designated " applied chemistry." Its recent expansion, however, by the 

 aid of chemistry, allows of its establishment as an independent branch 

 of knowledge, — a science, capable of a classification, not on the prin- 

 ciples of chemical science, but evolved from itself, by a comparison of 

 its subjects with each other. The main principle which should goyern 

 such classification is the object in view or the product to d>e made, 

 and, with this, the secondary arts necessarily or usually connected with 

 it. Thus, the making of soap, being an important art, and an exten- 

 sive manufacture, necessaiily includes the extraction and purification 

 of oils and fats, while perfumery and chandlery seem to follow in its 

 train in a natural order. The following i& an atte-inpt at such a classi- 

 fication of the subjects in chemical technology, and is the result of some 

 years' experience in lectures on the chemical arts delivered by the 

 writer before the Franklin Institute of Philadelphia. Doubtless, it 

 will be found imperfect, but it is fair to offer as an apology, the diffi- 

 culty experienced by the chemist in separating in his hand the compo- 

 sition and properties of bodies from their connection as objects of manu- 

 facture, and in breaking down long cherished associations of purely 

 chemical characteristics. 



Chemical affinity may be regarded as the force employed in the 

 chemical arts ; fuel and water, as the principal agents used to modify or 

 direct this force ; and the crude productions of the mineral, vege- 

 table, and animal kingdoms, as the materials subjected to action. 

 The air performs less important functions, as a direct agent ; but, in 

 conjunction with fuel, it is indirectly an indispensable agent, in 

 developing heat by the union of its oxygen with the carbon and hydro- 

 gen of fuel. Fuel is, however, the true agent in this case, practically 

 considered, because it can be handled, weighed, and measured, by the 

 artisan, and is indispensable in the reduction of metallic ores. "We 

 therefore regard fuel as the source of heat in the arts ; and since 

 the larger proportion of the more important technical processes are 

 more or less controlled by heat, it must be viewed as the principal agent 

 or modifier of affinity. Hence the sources and management of heat 

 should be the first subject treated of in a classified narration of technical 

 processes. It may be followed by its application to the warming of 

 buildings, which, in its manifold aspects of economy, convenience, 

 safety, and health of man, embraces the forms of apparatus in which it 

 is employed, and the subject of ventilation. 



More naturally connected with fuel than with any other depart- 

 ment of the arts, are the means of obtaining and of extinguishing 



