84 AGRICULTURAL CHEMISTRY 



89. Properties. Physically considered, chlorin is a 

 heavy, greenish yellow gas, with a penetrating, suffo- 

 cating odor. Chlorin gas is poisonous. Chemically, it 

 is an active element and has strong affinity for nearly all 

 other elements. It readily combines with metals, form- 

 ing chlorids, and light and heat are evolved during the 

 reaction. Chlorin is an active bleaching reagent, as it 

 changes the composition of vegetable dyes, thus destroy- 

 ing their color. Bleaching-powder is a mixture of cal- 

 cium hypochlorite and calcium chlorid, and when used 

 chlorin is liberated. Chlorin is also used as a disinfectant 

 and as a germicide, for it is destructive to life, particu- 

 larly to the lower forms. It is used extensively for both 

 bleaching and disinfecting purposes. Chlorin takes no 

 part directly in life processes, although its compounds, 

 particularly sodium chlorid, are necessary as mineral food 

 for animals. 



90. The Chlorin Group of Elements. Fluorin, chlo- 

 rin, bromin, and iodin form a natural group of elements, 

 known as the chlorin family. These elements are all 

 closely related. They form similar acids with H, and 

 similar salts with the metals. Some of the most im- 

 portant relationships and points of difference between 

 members of the chlorin family will be observed from the 

 following table : 



Physical 

 Element. At. wt. conditions. H compound. Na compound 



Fluorin 19 Light gas HF1 NaFl 



Chlorin 35.45 Heavy gas HC1 NaCl 



Bromin 79.95 Liquid HBr NaBr 



Iodin 126.85 Solid HI Nal 



