54 THE ALUMNI JOURNAL 



By heating Sulphur with Hydrogen, he obtained Hydrogen Sul- 

 phide, and was the first to investigate this ill-smelling compound 

 which gives the odor to the rotten egg. It is extensively employed 

 in laboratories as a group precipitant and reducing agent. It was 

 formerly used as an intestinal disinfectant, but fortunately "the 

 H„S wash-out" now belongs to the past. 



Scheele's name is intimately connected with the origin of pho- 

 tography, for it was he who scientifically investigated the darken- 

 ing action of sunlight on Silver Chloride. Further, by means of a 

 prism he threw the colored band of light upon a surface sensitized 

 with Silver Chloride, and noticed that the violet rays blackened 

 it more readily than the other colors of the spectrum. By utilizing 

 Scheele's experiments, Thomas Wedgwood of England produced 

 a photograph. 



Of course there is rarelv an absolutely new discovery in science, 

 and if we wish to go a little further back we can see Johann Schulze 

 working by a window — when the weather was warm and the sun 

 was shining. He wishes to treat some Calcium Carbonate with 

 Nitric Acid, and it so chances that the acid he uses has some silver 

 dissolved in it. He pours it on the chalk, the rays from the sun 

 fall on the mixture and turn it black, while Johann is highly 

 amazed to find that the effect of light is darkness ! 



If we travel back still more, we learn that some sort of a begin- 

 ning of photographic chemistry originated with the alchemists, 

 and if no one has yet demonstrated that Aristotle was the original 

 camera-fiend, some one will come to the rescue in the near future. 



Gladly giving due credit to all concerned, the fact remains that 

 Scheele was the first who applied chemical and spectrum analysis 

 to photography, which in the hands of the skilful has become a 

 noble science and a fine art. 



In 1778 he described a new method of procuring Calomel, the 

 most valuable of the mercurial preparations. 



He proposed a new way of making the powder of Algaroth, the 

 purgative and emetic named after the physician Algarotus of 

 Verona. 



He examined Molybdenite, which was thought to contain Lead. 

 He proved the contrary and secured from the mineral, Molybdic 

 Acid. 



In 1779 Scheele showed that Plumbago consists almost wholly 

 of Carbon. During this year he published records of his former 

 experiments- 



