It is sometimes stated that the low specific heat of mercury (033) is one of its special qualifications. Show that if the coefficients of expansion of the two liquids were the same, and two similar thermometer tubes were filled, one with each liquid, that filled with alcohol would require a greater quantity of heat to raise it through the same range of temperature unless the specific heat of alcohol were less than 528. [Sp. gr. of mercury 13.6; of alcohol 85.]

Camb. Schol. 1883.

101. A copper vessel containing a thermometer is at 12° C. 50 gm. of water at 60° are poured in, and the temperature after stirring is found to be 50°: find the thermal capacity or water-equivalent of the vessel and thermometer. Vict. Int. 1885.

102. State clearly the distinction between temperature and heat.

Twenty pound-degrees of heat are communicated to a metal vessel weighing 8 lbs., and containing 10 lbs. of water. If the specific heat of the metal be, in what proportion will the heat be divided between the water and the vessel, and what will be their rise of temperature?

Matric. 1884.

103. A bath being required at a temperature of 37° C., twelve pailsful of cold water at 10° are thrown into it. Hot water from a cistern at 55° is now poured in until the temperature of the bath is 25° C. If the water remaining in the cistern be now heated until it boils, show that the bath will be at the required temperature when four pailsful of the boiling water have been poured in, although its temperature falls 2° C. whilst the water in the cistern is being heated to the boiling point.

Camb. B.A. 1883.

104. 200 grammes of water at 99° C. are mixed with 200 cub. cm. of milk of density 103 at 15° C., contained in a copper vessel of thermal capacity equal to that of 8 grammes of water, and the temperature of the mixture is 57° C. If all the heat lost by the water is gained by

the milk and the copper, what is the specific heat of the milk? Matric. 1885.

105. What is the latent heat of fusion of a substance? A pound of ice at o° C. is thrown into 6 lbs. of water at 15° contained in a copper vessel weighing 3 lbs., and when the ice is melted the temperature of the water is 2° C find the latent heat of fusion of ice, the specific heat of copper being 0·095.

Matric. 1886.

106. Describe experiments illustrating the difference between temperature and heat.

In 100 grammes of boiling water (t = 100) there are placed 20 grammes of ice, and the temperature falls to 70° when the ice is just melted: what is the latent heat of fusion of ice, assuming no heat to be lost?

Matric. 1887.

107. Five hundred cubic centimetres of mercury at 56° C. are put into a hollow in a block of ice, and it is found that 159 grammes of the ice are liquified: find the specific heat of mercury. Glasgow M.A. 1882. 108. Three separate mixtures are made, namely—

(1) Water and snow,

(2) Water and salt,

(3) Snow and salt.

If all the materials were, before being mixed, at o° C., which mixture will be at the highest temperature and which at the lowest ? and why?

Matric. 1885.

109. Calculate the cooling effect of a cube of ice 2 ft. in the side, taken at o° C. and reaching 27° C. when its cooling power has been exhausted. (The coefficient of the expansion of water on changing into ice is, and the number of pounds in I cubic foot of water is 62.4.)

Edinb. M.A. 1882.

110. How many units of heat would cause a mixture of ice and water to contract by 50 cubic millimetres, if 100 cub. mm. of water at o° C. become 109 cub. mm. on freezing?

Matric. 1883.

111. Describe Bunsen's calorimeter. If 100 c.c. of water in freezing become 109 c.c. of ice, and the introduction of 20 grammes of mercury at 100° C., into a Bunsen's calorimeter cause the end of the column of mercury to move through 74 mm. in a tube one square millimetre in section, find the specific heat of mercury. (The heat required to melt one gramme of ice is 80 units.)

Matric. 1884.

112. A gramme of ice at o° contracts 0.091 c.c. in becoming water at o°. A piece of metal weighing 10 grammes is heated to 50°, and then dropped into the calorimeter. The total contraction is 063 c.c.: find the specific heat of the metal, taking the latent heat of ice as 80.

Vict. B.Sc. 1886.

113. Explain the formation of dew and hoarfrost. How do you account for the fact that a cloud is sometimes formed by the mixture of two quantities of air at different temperatures, although neither quantity is quite saturated before the admixture?

Matric. 1884.

114. Explain the principles on which the hygrometric state of the atmosphere is deduced from observations of the wet and dry bulb hygrometer, and show how the "constant of this instrument is experimentally found.

Int. Sc. Honours 1885.

115. Describe and discuss carefully the experiments you would make to determine the dew-point and the tension of aqueous vapour in the air.

Air from a space saturated with moisture is drawn into an aspirator of known volume through drying tubes : show carefully how, by means of this experiment and tables of the saturating tension of aqueous vapour, to determine the temperature of the space.

Camb. Schol. 1883. 116. What is meant by the statement that the latent heat of steam is 537?

One pound of saturated steam at 160° C. is blown into 19 lbs. of water at o° C., and the resulting tempera

ture is 32.765° C.: find the latent heat of steam at 160° C. Matric. 1883.

117. The specific heat of mercury is .03. A pound of steam at 100° C. is made to pass into a vessel containing 300 lbs. of mercury initially at o° C., the capacity for heat of the vessel being equal to 10 lbs. of water : what will be the temperature of the vessel and contents at the end of the experiment? Matric. 1884.

118. Distinguish between calorimetry and thermometry.

20 grammes of steam at 100° C. are condensed in a metal worm surrounded by 200 grammes of water at 10° C. If the water equivalent of the worm be 10 grammes, and the latent heat of steam be 536, determine the temperature to which the water is raised.

Matric. 1886.

in a closed It is found,

when the

119. I lb. of ice at 10° C. is placed vessel, and steam at 100° C. passed into it. after making the necessary corrections, that ice is just melted the resulting water weighs 1.134 lbs. ; and that when the temperature has risen to 100° C., it weighs 1.345 lbs. The specific heat of ice is .5: find the latent heats of water and steam. Camb. B.A. 1878.

CONDUCTIVITY AND THERMODYNAMICS.

Conductivity. The thermal conductivity (or coefficient of conductivity) of a substance is measured by the number of units of heat which pass in unit time across unit area of a plate whose thickness is unity, when its opposite faces are kept at temperatures differing by one degree. In the statement of this definition it is supposed that the flow of heat has become steady, and that the lines of flow of heat are perpendicular to the surfaces of the plate.

The thermal conductivity of a substance, in the C.G.S. system, is measured by the quantity of heat which flows per second, under these circumstances, across one square centimetre of a plate one centimetre in thickness, the opposite faces of the plate being kept at temperatures differing by 1° C.

The quantity of heat (H) which flows in a given time across a plate of given dimensions is inversely proportional to the thickness (d) of the plate, and is directly proportional to the area of its surface (s), to the difference of temperature (0) between its opposite faces, and to the time t. If the thermal conductivity of the substance be denoted by k,

1. A large tank is covered with a layer of ice 6 cm. thick and 24 square metres in area: assuming that the