ALDEHYDES. KETOXES. 489 



Glycerin-phosphoric acid is a clear colorless liquid which gradually 

 turns yellow, and decomposes slowly in the cold, more rapidly when 

 heated. It is a dibasic acid of decidedly acid taste and reaction. 

 The normal salts are soluble in water, but insoluble in alcohol, and 

 generally have an alkaline reaction. The usual reagents for phos- 

 phoric acid do not affect the solution of glycerin-phosphoric acid in 

 the cold. The calcium, potassium, sodium, lithium, iron, and quinine 

 salts of the acid have been introduced into medicine. 



Calcium glycerin -phosphate, C 3 H 5 (OH). 2 CaPO 4 + H,O, is a white 

 crystalline powder, soluble in 20 parts of water, but less soluble in hot water. 

 It is neutral to litmus, but the commercial product is sometimes acid. It loses 

 its water of crystallization at or above 130 C. 



Sodium glycerin-phosphate, C 3 H 5 (OH) 2 .Na 2 PO 4 + H 2 O, is obtained 

 by neutralizing glycerin-phosphoric acid. It occurs in the market as a 50 per 

 cent, solution of a clear, light yellow color. 



44. ALDEHYDES. KETONES. 



Aldehydes. The name aldehyde is derived from alcohol dehydro- 

 genatum, referring to its method of formation, viz., by the removal 

 of hydrogen from alcohols, as, for instance : 



C 2 H 6 O 2H = C 2 H 4 O. 

 Ethyl alcohol. Acetic aldehyde. 



This removal of hydrogen may be accomplished by various methods, 

 as, for instance, by oxidation of alcohols, when one atom of oxygen 

 combines with two atoms of hydrogen, forming water, while an alde- 

 hyde is formed at the same time. Aldehydes, when further oxidized, 

 are converted into acids ; aldehydes are, consequently, the interme- 

 diate products between alcohols and acids, and are frequently looked 

 upon as the hydrides of the acid radicals. The constitution of acetic 



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

 difference between monatomic, diatomic, and triatomic alcohols? How do 

 alcohols occur in nature ? By what processes may alcohols be formed arti- 

 ficially, and how may they be separated from their combinations ? State the 

 general properties of alcohols. Mention names and composition of the first 

 five members of alcohols of the general composition C n H2n+iOH. By what 

 process is methyl alcohol obtained, under what other names is it known, and 

 what are its properties? Describe the manufacture of pure alcohol from 

 sugar. Give the alcoholic strength of the alcohol and diluted alcohol of the 

 U. S. P., and also of spirit of wine, proof-spirit, light wines, heavy wines, beers, 

 and spirits. What are the general properties of common alcohol ? How is 

 alcohol denatured ? What is glycerin, how is it found in nature, how is it 

 obtained, and what are its properties ? 



