In the 196s, Professor Black, a Scottish chemist, was also interested in the nature of heat. In industrialized Glasgow and Edinburgh, the problem of heat is particularly important, because Scotland and England were the first British chemist Blake to separate carbon dioxide and demonstrate the characteristics of carbon dioxide (which he called "fixed air"). The merger in 177 brought a rich economy, which developed a good market for the local whisky industry. Large breweries use a lot of fuel, generate a lot of heat, turn liquid into steam, and then have to release this heat to condense steam into liquid. In order to manage the brewery economically, it is absolutely necessary to know how much heat is involved in these processes. In fact, a lot of heat needs to be released from the steam, which directly affects the income of the brewery.
Blake often says that he can't understand why the managers of breweries don't pay more attention to the relevant scientific principles, which obviously have a very important impact on their livelihood. However, traditionally, the connection between pure science and technological progress is rarely realized and rarely supported. Even today, whenever business needs to cut back, the research and development department is often the first target to be cut, and universities are often the target to cut their budgets during the economic recession.
Blake never published his speech, in which he thoroughly discussed his thoughts, but his editor, John Robison (1739-185), published materials selected from Blake's notebooks and his own records:
"In view of the fact that the snow on the sunny winter mountains does not melt immediately, and the cold night does not immediately cover the pond with thick ice, Dr. Blake is convinced that a lot of heat has already occurred. On the other hand, when water slowly turns into ice, a lot of heat is released from the water. Because, in the process of thawing, when the thermometer moves from air to snow melting, it often drops; In severe cold, when a thermometer is inserted into frozen water, it tends to rise. Therefore, in the first case, snow gets heat; In the latter case, water is releasing heat again. "
In p>1762, during the gathering of the University Philosophy Club, some professors met informally in Glasgow, and Blake further discussed his views. He pointed out that when ice melts, it doesn't change its temperature. However, the substance near the ice becomes colder, but the temperature of the ice doesn't rise. What's going on here? Has the heat gone away? Warren Hite once observed that water can be cooled below freezing point without freezing, but at this time there should be no disturbance to water, otherwise it will freeze immediately. When this happens, the temperature actually rises! Therefore, when water freezes, that is, its state changes from liquid to solid, it gives off heat. Blake saw that water remained liquid because it contained a certain amount of heat. When the heat is released, the liquid disappears, and the liquid water becomes solid ice.
Because the heat in liquid water will not be displayed on the thermometer, Blake calls it "latent heat", which means that it exists but cannot be measured in the usual way.
Blake also proposed a method to measure latent heat. He measured the heat needed to melt a certain amount of ice, and then applied this heat to the water obtained after the ice melted, and found that its temperature rose by 14 F.
from 1762 to 1764, Blake extended the concept of latent heat of ice to the similar phenomenon that water changed into steam. He found that it takes five times as long to change boiling water into steam with the same firepower as it takes to heat water from room temperature to boiling point.
At this time, an unexpected new friend joined the research. This new friend is Watt, a technician who makes instruments for universities. Watt designed a device to demonstrate the concept of latent heat discussed by Blake in class and provide experimental evidence for it. An unexpected surprise is that Watt, inspired by the theory he got from Blake, successfully invented a new device for the steam engine he was repairing: the separation condenser. As a result, this invention has become the key to improve the efficiency of steam engine and make it the key to obtain enough economic energy for transportation and industry. Watt's steam engine uses coal or coke as fuel, so the factory can be set up anywhere, away from the river, and the factory opened by water power must be located by the river. Steam engines were soon used in almost all industries, from coal mines to smelters to textile mills, and later trains and ships.
The high-pressure coal car engine designed by Loewis Ke may be similar to the steam carriage he built based on Watt's steam engine in 181. Black is very satisfied with this. He is happy to tell the students about Watt's achievements. When Watt applied for a patent in 1769, he got his due reward. Robinson wrote: "Dr. Black has never been so happy, as if these benefits were for himself. ..... Both friends think that this successful research is the happiest thing in their lives. "
earlier, Blake also proved that different substances with the same mass need different heat (specific heat) to raise them to the same temperature. Or, to put it another way, when two different substances with the same weight and different temperatures are put together, the equilibrium temperature is not the midpoint of the two temperatures. In other words, the same heat acts on two different substances, resulting in different temperature changes. Blake believes in the theory of hot fluid, so when he comes to the conclusion that different substances have different so-called "specific heat", he is even more convinced that Bacon's (and later Renford's) thermodynamic theory is contradictory to the existence of specific heat. Unfortunately, this view later became a case in the history of science, which shows that correct science sometimes seems not to support an effective theory.