Editing Latent heat (section)

==== Quantifying latent heat ====
In 1762, Black announced the following research and results to a society of professors at the University of Glasgow.<ref name=":2">{{Cite book |last=Black |first=Joseph |author-link=Joseph Black |url=https://books.google.com/books?id=lqI9AQAAMAAJ&pg=PA120 |title=Lectures on the Elements of Chemistry: Delivered in the University of Edinburgh |date=1807 |publisher=Mathew Carey |editor-last=Robinson |editor-first=John |edition= |pages=120 |language=en}}</ref> Black had placed equal masses of ice at 32&nbsp;°F (0&nbsp;°C) and water at 33&nbsp;°F (0.6&nbsp;°C) respectively in two identical, well separated containers. The water and the ice were both evenly heated to 40&nbsp;°F by the air in the room, which was at a constant 47&nbsp;°F (8&nbsp;°C). The water had therefore received 40&nbsp;–&nbsp;33&nbsp;=&nbsp;7 “degrees of heat”. The ice had been heated for 21 times longer and had therefore received 7&nbsp;×&nbsp;21&nbsp;=&nbsp;147 “degrees of heat”.{{refn|group=lower-alpha|These “degrees of heat” were context-dependent and could only be used when circumstances were identical—except for the one differing factor to be investigated. When Black investigated specific heat, the “degrees of heat” were based on change in temperature multiplied by mass. When Black investigated latent heat, they were based on change in temperature multiplied by time passed. Clearly these units were not equivalent.}} The temperature of the ice had increased by 8&nbsp;°F. The ice had thus absorbed 8 “degrees of heat”, which Black called ''sensible heat'', manifest as a temperature increase, which could be felt and measured. In addition to that, 147 – 8 = 139 “degrees of heat” were absorbed as ''latent heat'', manifest as phase change rather than as temperature change.<ref name=":12">{{Cite book |last=Ramsay |first=W. |author-link=William Ramsay |url=https://books.google.com/books?id=micIAAAAIAAJ&pg=PA44 |title=The life and letters of Joseph Black, M.D. |publisher=Constable |year=1918 |pages=44}}</ref><ref>{{Cite book |last=Black |first=Joseph |author-link=Joseph Black |url=https://books.google.com/books?id=lqI9AQAAMAAJ&pg=PA115 |title=Lectures on the Elements of Chemistry: Delivered in the University of Edinburgh |date=1807 |publisher=Mathew Carey |editor-last=Robinson |editor-first=John |edition= |pages=115–117 |language=en}}</ref> 

Black next showed that a water temperature of 176&nbsp;°F was needed to melt an equal mass of ice until it was all 32&nbsp;°F. So now 176&nbsp;– 32&nbsp;=&nbsp;144 “degrees of heat” seemed to be needed to melt the ice. The modern value for the heat of fusion of ice would be 143 “degrees of heat” on the same scale (79.5 “degrees of heat Celsius”).<ref name=":13">{{Cite book |last=Ramsay |first=W. |author-link=William Ramsay |url=https://books.google.com/books?id=micIAAAAIAAJ&pg=PA45 |title=The life and letters of Joseph Black, M.D. |publisher=Constable |year=1918 |pages=45}}</ref><ref name=":2" /> 

Finally, Black increased the temperature of a mass of water, then vaporized an equal mass of water by even heating. He showed that 830 “degrees of heat” was needed for the vaporization; again based on the time required. The modern value for the heat of vaporization of water would be 967 “degrees of heat” on the same scale.<ref name=":14">{{Cite book |last=Ramsay |first=W. |author-link=William Ramsay |url=https://books.google.com/books?id=micIAAAAIAAJ&pg=PA45 |title=The life and letters of Joseph Black, M.D. |publisher=Constable |year=1918 |pages=45–46}}</ref>