178 CHEMISTRY. 



twenty grains* of citric acid (acid of lemons) in two 

 separate glasses, mixing them, and then drinking 

 them in a state of effervescence. 



Cream, 



Cream consists of three ingredients : viz. 

 Butter ... 4-5 

 Cheese . . . 3 '5 

 Whey ... 92- 



100 parts.f 

 Butter contains from 40 to 65 per cent, of suet. 



Oxalic Acid. 



The oxalic acid is found in some fruits, and in the 

 juice of the wood sorrel (hence its name) and rhu- 

 barb ; but it is most readily procured by the action 

 of nitric acid on sugar, and has from this circum- 

 stance been termed the acid of sugar. 



The Metals. 



The metals are forty-two in number, and weigh, 



compared with water taken as 1 ; viz. 



Platinum . . 21' Silver . . 10*30 

 Gold . . . 19-30 Sodium . . 0-972 

 Mercury . . 13-50 Potassium . 0-865 



Platinum is the heaviest body in nature. 



The Refining of Metals. 



All processes for refining metals by fire must be 

 performed by taking advantage of some property in 



* In the sodaic powders of the shops, tartaric acid, on account 

 of its cheapness, is too often substituted. 



f Cheese, besides other ingredients, contains a horny sub- 

 stance and the lactic acid ; so that with cream to our tea we swal- 

 low butter, cheese, suet, whey, lactic acid, and horns. 



