THE LIFE OF KARL WILHELM SCHEELE xxv 



Decomposition of Neutral Salts by Unslaked Lime and Iron. 

 At this period he made several important observations 

 during his investigation of this subject. 



Oxygen in the air Daily percentage. During the same 

 year he published a record of determinations of the amount of 

 pure air, i.e. of oxygen contained in the atmosphere, which 

 he made every day during the entire year of 1778. How 

 many chemists of the present day would care to undertake 

 sucli an onerous task. 



1780. Milk, Sugar of Milk, Lactic Acid, Mucic Acid. 

 In this year he published his Essays on Milk, and Sugar of 

 Milk. In these essays are detailed many reactions unknown 

 to many of the chemists of the present day, who think 

 a knowledge of the ringing of the changes on the coal tar 

 colours the be-all and the end-all of chemistry, and think 

 such a commonplace subject as the chemistry of milk beneath 

 contempt. Nevertheless, these essays are amongst the earliest 

 examples of the chemical examination of animal fluids, and 

 any chemist desiring to enter upon the study of such fluids 

 could not do better than to repeat Scheele's experiments upon 

 milk and sugar of milk. He showed the acidity of milk was 

 caused by a peculiar acid we now know as the lactic acid ; again 

 he prepared mucic acid by boiling milk sugar with nitric acid. 



1781. Scheelite, Tungstate of Lime. In this year he 

 determined the composition of the mineral tungsten now 

 known as scheelite. This he found to consist of lime in com- 

 bination with a peculiar acid, tungstic acid. It may be 

 mentioned here that tungstate of soda is much used in fire- 

 proofing muslin, etc. Here, then, is another benefit to 

 humanity indirectly due to Scheele. 



1782. Ether. We again find him in this year applying 

 his experimental knowledge to perfecting the making of 

 substances used in his profession. 



