/oss/taxonomy/term/3541/all en /oss/article/history/powder-sympathy <p>Four hundred years ago Belgian physician Johann Baptist Van Helmont was persecuted by the Roman Catholic Church for promoting the use of the “Powder of Sympathy” that was supposed to treat wounds by applying it to a dressing that had previously covered the wound. The exact nature of the substance varied, but iron or copper sulfate seem to have been common ingredients. This folly was first proposed by physician and scoundrel Sir Kenelm Digby, but Van Helmont bought into the idea. Somehow the effect of the powder on the bloody dressing was to be communicated to the blood still in the body.</p> Fri, 25 Feb 2022 18:33:41 +0000 Joe Schwarcz PhD 9037 at /oss /oss/article/you-asked/there-difference-between-real-snow-and-artificial-snow <p>Snow-making machines actually make tiny beads of ice, each one about one ten-thousandth of an inch in diameter. Water is sprayed from a hose together with compressed air. The air is needed because as it quickly expands, its temperature drops since it has to do work by pushing away air molecules. This cooling helps freeze the water. As the water freezes, it releases heat. This should be obvious when we realize that in order to melt ice, we have to add heat. The heat released is then taken up by the expanding compressed air. This is why the "snow-making" pipes are always high in the air. If t</p> Thu, 17 Feb 2022 15:29:52 +0000 Joe Schwarcz PhD 9027 at /oss /oss/article/history/no-sympathy-powder-sympathy <p>Four hundred years ago Belgian physician Johann Baptist Van Helmont was persecuted by the Roman Catholic Church for promoting the use of the "Powder of Sympathy", a concoction that was supposed to treat wounds by applying it to a dressing that had previously covered the wound. The exact nature of the substance varied, but iron or copper sulfate seem to have been common ingredients. This silliness was first proposed by physician and scoundrel Sir Kenelm Digby, but Van Helmont bought into the idea.</p> Thu, 06 Dec 2018 16:50:49 +0000 Joe Schwarcz PhD 7477 at /oss