ix SCIENTIFIC MOTIVE 251 



during a purely scientific investigation. Referring to 

 this, a great chemist once remarked : 



Whenever one of your chemical friends, full of enthusiasm, 

 exhibits and explains to you his newly- discovered compound, 

 you will not cool his noble ardour by asking him that most terrible 

 of all questions, " What is its use ? Will your compound bleach 

 or dye ? Will it shave ? May it be used as a substitute for 

 leather ? " Let him quietly go on with his work. The dye, 

 the leather, will make their appearance in due time. Let him, 

 I repeat, perform his task. Let him indulge in the pursuit of 

 truth of truth pure and simple of truth not for the sake of 

 Mauve let him pursue truth for the sake of truth. Prof. A. W. 

 von Hofmann. 



The discovery of oxygen gas by a poor Swedish 

 apothecary, Scheele, and independently by the English- 

 man, Joseph Priestley, son of a humble cloth-dresser, 

 was one of the most important ever made in chemistry, 

 but more than a century elapsed before practical value 

 was given to it by the use of oxygen with hydrogen in 

 the oxy-hydric process of cutting metals, and in many 

 other arts. Chlorine another gas discovered by Scheele 

 not only influenced the progress of pure chemistry but 

 also now plays an important part in practical affairs. 

 It is used for bleaching straw, paper and other materials, 

 and is essential to the manufacture of chloroform, 

 which could never have been discovered but for Scheele's 

 work. It is used extensively in the chlorination process 

 for the extraction of gold from its ores ; and the noxious 

 green gas first produced with simple apparatus in a 

 little room of an apothecary's shop has thus become a 

 valuable servant of a great industry as well as a diabolical 

 weapon of warfare. One of the deadliest poisons known 

 to chemistry, potassium cyanide, when in dilute solution, 

 will dissolve natural gold ; and here again a laboratory 

 observation has given rise to an important practical 



