314 CONSIDERATION OF CARBON COMPOUNDS. 



Boroglycerin is made by heating a mixture of boric acid and gly- 

 cerin, when the compound C 3 H 5 BO 3 is obtained. 



Analytical reactions. 



1. A borax bead immersed for a few minutes in a solution of 

 glycerin (made slightly alkaline with potassium hydroxide) imparts 

 a green color to a non-luminous flame, owing to the liberation of 

 boric acid. 



2. Glycerin slightly warmed with an equal volume of sulphuric 

 acid should not turn dark, but, on further heating, the characteristic, 

 irritating odor of acrole'in is noticed. 



3. Fehling's solution (see index) should not cause a red precipita- 

 tion on heating, indicating the absence of glucose and dextrin. 



Nitre-glycerin, C 3 HJNO 3 ) 3 ((?^cen/ n'-mrafe, Glonoin). When 

 glycerin is treated with nitric acid, or, better, with a mixture of con- 

 centrated sulphuric and nitric acids, chemical action takes place 

 resulting in the formation of glyceryl mono-nitrate, or tri nitrate, 

 substances belonging to the group of compound ethers, the constitu- 

 tion of which will be explained later. 



C 3 H 5 (OH) 3 + 3HN0 3 = C 3 H 5 (N0 3 ) 3 + 3H 2 O. 



The tri-nitro-glycerin is the common nitro-glycerin, a pale-yellow 

 oily liquid, which is nearly insoluble in water, soluble in alcohol, 

 crystallizes at 20 C. ( 4 F.) in long needles, and explodes very 

 violently by concussion ; it may be burned in an open vessel, but 

 explodes when heated over 250 C. (482 F.). 



Spirit of glonoin is an alcoholic solution of nitro-glycerin, con- 

 taining of this substance 1 per cent. 



Dynamite is infusorial earth impregnated with nitro-glycerin. 



Phenols. The substances termed phenols are formed by replacement of 

 hydrogen by hydroxyl in the aromatic hydrocarbons of the benzene series ; 

 they have the constitution of alcohols, but are not alcohols in the sense in 

 which this term is used. The more important substances belonging to this 

 group will be considered later. 



QUESTIONS. 401. What is the general constitution of alcohols, and what is 

 the difference between monatomic, diatomic, and triatomic alcohols? 402. How 

 do alcohols occur in nature? 403. By what processes may alcohols be formed 

 artificially, and how may they be separated from their combinations? 404. 

 State the general properties of alcohols. 405. Mention names and composition 

 of the first five members of alcohols of the general composition Cn Ebn 4-iOH. 



