This section is from the book "The Building Trades Pocketbook", by International Correspondence Schools. Also available from Amazon: Building Trades Pocketbook: a Handy Manual of reference on Building Construction.
When properly burned, quicklime should possess the following qualities: It should be in lumps, free from cinders. and with little or no dust; it should slake readily in water to a smooth, impalpable paste, without residue; and it should dissolve in soft water if enough is added.
Lime weighs about 66 lb. per bu., or about 53 lb. per cu. ft. One barrel of lime, weighing 230 lb., will make about 2 1/4 bbl., or .3 cu. yd. of stiff paste. In l-to-3 mortar, 1 bbl. of unslaked lime will make about 6 3/4 bbl. of mortar; or 1 bbl. of lime paste will make about 3 bbl. of mortar. For a l-to-2 mortar, about 1 bbl. of quicklime to 5 or 5 1/2 bbl. of sand are used.