Abstract: A method for measuring the volume of a sample comprises measuring the weight of the sample by means of a balance within a sealed vessel containing a first gas; then replacing the first gas in the vessel with a second gas having a density different from that of the first gas; and then measuring the weight of the sample by means of the balance within the sealed vessel containing the second gas to determine a change of weight of the sample corresponding to the change of the gas in the sealed vessel. Then the volume of the sample is calculated according to Archimedis' principle as a function of the value of the difference between the density of the first gas and the second gas, and the value of the change of weight of the sample corresponding to the change of the gas. An apparatus for measuring the volume of the sample is also disclosed.

Abstract: A process for producing an artificial light-weight aggregate comprising SiO.sub.2, Al.sub.2 O.sub.3, Fe.sub.2 O.sub.3 and at least one oxide selected from the group consisting of MgO and CaO which has an absolute dry specific gravity of not higher than 1.5, a crushing strength of not less than 55 kfg/cm.sup.2 and a 24 hour water-absorption ratio of not greater than 2.4%. The process comprises granulating a raw powder material comprising SiO.sub.2, Al.sub.2 O.sub.3, Fe.sub.2 O.sub.3 and at least one oxide selected from the group consisting of MgO and CaO, in which the total amount of SiO.sub.2 and Al.sub.2 O.sub.3 is from 75 to 92 wt. %, the weight ratio of Al.sub.2 O.sub.3 /SiO.sub.2 is from 0.25 to 0.70, and the total amount of Fe.sub.2 O.sub.3 and MgO and/or CaO is from 6-20 wt. % and containing at least 80% by weight of a coal ash having a Blaine specific surface area of 2,000 to 9,000 cm.sup.2 /g to give granules having an average apparent specific gravity of 1.1 to 1.8 and a crushing strength of 0.