Phosphate of lime, as it exists in bones, consists of one atom of phosphoric acid and three atoms of lime. It may be represented as { Lime Phosphoric acid { Lime { Lime By adding a proper quantity of sulphuric acid with this, it becomes _super_-phosphate of lime; that is, the same amount of phosphoric acid, with a smaller proportion of lime (or a _super_-abundance of phosphoric acid), the sulphuric acid, taking two atoms of lime away from the compound, combined with it making sulphate of lime (plaster). The changes may be thus represented. {Phosphoric acid} Super-phosphate Phosphate of lime {Lime } of lime. {Lime} {Lime} Sulphate of lime. Sulphuric acid} Super-phosphate of lime may be made from whole bones, bone dust, bone-black, or from the pure ashes of bones. [How should sulphuric acid be applied to whole bones? What is the necessity for so large an amount of water?] The process of making it from whole bones is slow and troublesome, as it requires a long time for the effect to diffuse itself through the whole mass of a large bone. When it is made in this way, the bones should be _dry_, and the acid should be diluted in many times its bulk of water, and should be applied to the bones (which may be placed in a suitable cask, with a spiggot at the bottom), in quantities sufficient to cover them, about once in ten days; and at the end of that time, one half of the liquid should be drawn off by the spiggot. This liquid is a solution of super-phosphate of lime, containing sulphate of lime, and may be applied to the soil in a liquid form, or through the medium of a compost heap. The object of using so much water is to prevent an incrustation of sulphate of lime on the surfaces of the bones, this must be removed by stirring the mass, which allows the next application of acid to act directly on the phosphate remaining. The amount of acid required is about 50 or 60 lbs. to each 100 lbs. of bones. The gelatine will remain after the phosphate is all dissolved, and may be composted with muck, or plowed under the soil, where it will form ammonia. [May less water be employed in making super-phosphate from bone dust or crushed bones?] _Bone dust_, or _crushed bones_, may be much more easily changed to the desired condition, as the surface exposed is much greater, and the acid can act more generally throughout the whole mass. The amount of acid required is the same as in the other case, but it may be used _stronger_, two or three times its bulk of water being sufficient, if the bones are finely ground or crushed--more or less water should be used according to the fineness of the bones. The time occupied will also be much less, and the result of the operation will be in better condition for manure.