_If the solid is soluble in water, or has a tendency to float_, some liquid other than water is used. Paraffin oil or oil of turpentine will do. The process is as follows:--The weight of the dry and empty bottle having been determined, add a sufficiency of the substance and weigh again to find how much has been added. Fill up with paraffin oil and weigh again. Clean out the substance by rinsing with paraffin; fill up and weigh. Calculate the sp. g. as if water had been used, and multiply by the sp. g. of the paraffin. For example: 1. Weight of bottle 39.299 grams 2. " " bottle and nitre 57.830 " 3. " " bottle and paraffin 73.146 " 4. " " bottle and paraffin and nitre 84.665 " 5. " " bottle and water 81.884 " First from (1),(3), and (5), calculate the sp. g. of the paraffin as already shown. It will be 0.7948. Deduct (1) from (2) to get the weight of the nitre: 57.830 grams 39.299 " ------ 18.531 " add this to (3): 18.531 grams 73.146 " ------ 91.677 " and deduct (4) to find the weight of the equal bulk of paraffin. 91.677 grams 84.665 " ------ 7.012 " divide the weight of the nitre by the weight of the paraffin: 7.012)18.531(2.6427 ------ ...... The sp. g., taking paraffin as the standard instead of water, is 2.6427. Multiply this by the sp. g. of paraffin, 0.7948, and the result is 2.1004 as the sp. g. of nitre compared with water. Similarly, a sp. g. compared with water at say 50° C. can be converted into one compared with water at standard temperature, by multiplying by the sp. g. of water at 50° C. The following table gives the sp. g. of water at various temperatures:-- -----------+------++-----------+------++-----------+------- Degrees | || Degrees | || Degrees | Centigrade.|Sp. G.||Centigrade.|Sp. G.||Centigrade.|Sp. G. -----------+------++-----------+------++-----------+------- 4° |1.0000|| 20° |0.9982|| 40° |0.9923 10° |0.9997|| 25° |0.9971|| 50° |0.9881 15° |0.9991|| 30° |0.9957|| 100° |0.9586 -----------+------++-----------+------++-----------+------- If, for example, a substance at 50° C. has a sp. g. of 0.9010 as compared with water at 50° C., it will have (compared with water at 4° C.) a sp. g. of 0.9010×0.9881; or 0.8903. The figures 0.8903 represent the sp. g. of the substance at 50° C. compared with water at 4° C. Except in comparing the sp. gravities of the same substance at different temperatures, a calculation of this kind serves no useful purpose.