PHOTO-SYNTHESIS 103 



acid is a strong volatile acid, of pungent smell, and very 

 irritating in contact with scratches on the skin. 



Acetic Acid, CH3.COOH, occurs in many plants, 

 is a common product of fermentation, and is produced in 

 the distillation of wood (see p. 129), from which latter 

 source most of the acid of commerce is obtained. It can 

 be produced from coniferous sawdust, saturated with sodium 

 hydroxide, and subjected to steam and air at 120° Cent. 

 It is a mono-basic acid, volatile, has a fairly strong smell, 

 and forms well-recognized salts, mostly soluble in water. 

 The purer acid is used for pickles and other food purposes. 

 Calcium acetate is used for the manufacture of acetone, and 

 for mordanting cotton goods. 



Lactic Acid, or hydroxy propionic acid, CH3.CH(0H).- 

 COOH, is a common product of fermentation, and is also 

 found in muscular tissue. It can be manufactured from 

 glucose, chalk, and sour milk. It is not volatile, but on 

 concentration the solution forms a lactone by loss of water. 

 This ability to split off water makes it a valuable hydrolytic 

 agent. In free and uncontrolled fermentation the develop- 

 ment of lactic acid proceeds best in the presence of much 

 nitrogenous material. The salts of lactic acid crystallize 

 poorly. 



Oxalic Acid, (COOH)2.2H20.— The oxidation of almost 

 any organic substance will produce some oxalic acid. It 

 is almost universally found in plants, but beet leaves, 

 rhubarb leaves, and sorrel contain especially large quantities. 

 Oxalic acid is manufactured from coniferous sawdust, 

 saturated with sodium hydroxide, subjected to steam, and 

 a large proportion of air, at 300° Cent. The sodium 

 oxalate so formed is treated with sulphuric acid. It is a 

 di-basic acid, non-volatile, forms good crystalline salts 

 with the alkalies, whilst its calcium salt is marked by its 

 special insolubility, a property which enables plants to 

 deposit insoluble calcium oxalate in their tissues as a means 

 of getting rid of excessive quantities of this acid. Calcium 

 oxalate is insoluble in any of the acids commonly found in 

 plants. Oxalic acid is poisonous to both plants and animals. 



