on black magnesia, or the binoxide of manganese, which M. Clève suggests may have been the most important that he made, he discovered that the basis of the mineral was a new fundamental body, manganese; that it contained, as an impurity, a new earth, baryta, and that when it was treated with muriatic acid another new substance was evolved, chlorine. Further experiments with the last substance revealed its bleaching qualities, which have been so extensively applied in the arts. Finding that the presence of white arsenic helped the solution of the oxide of manganese in acids, he experimented with that body, and discovered the more important arsenical compounds. Scheele discovered that phosphorus was the cause of cold-shortness in iron, and showed that argillaceous earth was distinct from silicious earth, and not an acid-worked modification of it, as had been supposed. He experimented with plumbago, and found that it was "a kind of mineral sulphur or carbon, composed of carbonic acid and a large quantity of phlogiston," or, as we would express it, of carbon, and showed that it was the insoluble substance that occurred in cast-iron, thus opening the way to the further researches that have been made in the differences between iron, cast-iron, and steel, which, still under prosecution, lie at the foundation of our greatest industries. Connected with this investigation, on account of the resemblance of the minerals to graphite, were his researches in molybdenum and in wolfram. The last resulted in the discovery of the metal tungsten, for which the name Scheelium has been proposed.
Very little was known of organic compounds in Scheele's time. It is one of his great titles to merit that he first opened the way to the rich field of the fruitful and enriching discoveries that distinguish the medical and industrial chemistry of our day. The first in order of his researches in this line is his memoir on Prussian-blue, which well illustrates the readiness with which, bringing his extraordinary penetration to bear, he was able to arrive at the truth. In the course of his research he obtained a colorless liquid, which he described as "a substance having a curious odor, but not disagreeable, with a taste somewhat like that of sugar, which heated the mouth slightly and provoked coughing." He little imagined that he had in his hands one of the deadliest poisons known, prussic acid; and we shudder when we think how near it might have come to making an end of him. His researches on the different species of alcohol, described in 1782, indicate that he obtained aldehyde, a substance which has since been the starting-point for numerous important combinations, but of which the discovery is attributed to Liebig, in 1835; he appears also to have encountered chloral in his researches.
The preparations made in his shop led Scheele, in 1783, to the discovery of glycerine, which was at first called Scheele's sweet principle of oils. Boiling oxide of lead with water and oils, he obtained a plaster which he called a kind of hard soap, and which was not
