The water in the tank is heated by injecting steam, or by burners under the tank. As the tank holds about 300 pounds of water the work is not subject to sudden changes of temperature, and little trouble has been experienced in raising and maintaining the temperature of the water, especially when steam is used. An electric motor, or a small water-motor with only a very moderate head of water, will furnish ample power. =130. Comparison of Results.=—The following data show the results obtained by the digester as compared with those furnished by the official method, temperature and time of digestion being the same in each instance. AMMONIUM CITRATE SOLUTION ON PHOSPHATES. ------------------------------------------------------------------- Time Total Removed Removed of phos. by official by Substance. treatment. acid. method. digester. Per cent. Per cent. Per cent. ------------------------------------------------------------------- ½ hour 27.67 10.59 14.52 1 “ 12.21 14.82 2 hours 14.61 17.56 Steamed bone, 3½ “ 16.48 18.53 5 “ 17.94 20.22 7½ “ 18.99 20.25 10 “ 19.73 21.18 ------------------------------------------------------------------- ½ hour 13.86 4.43 4.11 1 “ 8.28 6.82 2 hours 10.34 9.76 Marl, 3½ “ 11.00 11.31 5 “ 11.80 11.83 8 “ 12.51 12.64 10 “ 12.58 13.00 ------------------------------------------------------------------- ½ hour 19.38 12.09 12.28 1 “ 12.47 12.40 Acidulated bone, 2 hours 12.20 12.43 3½ “ 12.40 12.24 5 “ 12.43 12.26 ------------------------------------------------------------------- Bone, ½ hour 21.40 6.97 8.48 Ammoniated dissolved bone, ½ “ 18.22 9.28 10.63 Cottonseed-meal and castor pomace, ½ “ 2.52 0.23 0.25 Phospho bone, ¼ “ 16.55 7.06 7.21