244 ANNUAL REPOKT SMITHSONIAN INSTITUTION, 1912. 



tinuous process, such as is possible in the bituminous coal-tar mdustry, 

 has not yet been found. A large number of patents have been taken 

 out for apparatus intended to solve this problem, but none of them 

 have proved satisfactory in practice. 



ORGANIC INTERMEDIATE PRODUCTS. 



The conversion of the aromatic hydrocarbons into intermediate 

 products necessary for the color industry is almost always carried out 

 by treatment with concentrated sulphuric and nitric acid and subse- 

 quent reduction of the thus obtamed nitrocompound by means of 

 metals, metalous oxids, and metal sulpliides. In the production of 

 ammes, iron is the principal agent of reduction, wliile zinc and tin are 

 mostly used in the production of azo compounds. The electrolytic 

 reduction has not proved useful for these processes. 



The methods of producing nitro and amido compounds have been 

 very httle changed as far as chemical operations are concerned, but 

 with the increase of their production their poisonous properties became 

 more and more apparent and forced the manufacturer to modif}^ the 

 processes so that they could be carried out in tightly closed vessels in 

 order to protect the life and health of the workmen. 



In Germany legislation has been recently enacted, based on the 

 experience of the individual factories, which lays down rules and 

 regulations for strict observance. 



Several trinitro compounds have been shown to be good explosives, 

 and, like trinitrotoluene, are now largely employed as substitutes of 

 picric aicd in the manufacture of explosives. 



The introduction of oxy groups mto the molecule is mostly brought 

 about by melting sulpho acids with alkaUes, and, according to more 

 recent methods, with alkaUne-earth metals, such as calcium and 

 barium hydrate. Since chlorine, produced electrolytically, is obtain- 

 able in unhmited quantities and chemically pure, chlorine substitution 

 derivatives of the hydrocarbons have been emplo3^ed for all kmds of 

 synthetical purposes. Many of these chlorine derivatives can not only 

 be converted into oxy-derivatives by melting with alkalies, but, like 

 paranitro-chlorbenzole, they also directly exchange their chlorine for 

 an amido group when treated with ammonia or its derivatives. Colors 

 also often change their shade when a halogen atom is introduced into 

 their molecule and acquire more valuable properties. Chlorine has 

 therefore proved exceedingly useful in the preparation of intermediate 

 products and will undoubtedly become of still greater service in the 

 future. 



In the naphthalene series the method discovered by Bucherer 

 and Lepetit for the conversion of the hydroxyl group into the 

 amido group and vice versa, employing sulphurous acid esters, 

 has proved of great practical value. Phosgene, too, is to-day 



