_Showing the bulk-percentages of barium sulphate (BaSO_{4}) and the corresponding gravimetric percentages and grains per fluidounce of sulphuric acid (SO_{3}).--(Purdy.)_ Bulk-percentage | Percentage | Gr. Per Oz. of BaSO_{4}. | SO_{3}. | SO_{3}. ----------------+------------+------------ 1/8 | 0.04 | 0.19 1/4 | 0.07 | 0.34 3/8 | 0.1 | 0.48 1/2 | 0.13 | 0.62 5/8 | 0.16 | 0.77 3/4 | 0.19 | 0.91 7/8 | 0.22 | 1.06 1 | 0.25 | 1.1 1¼ | 0.31 | 1.49 1½ | 0.37 | 1.78 1¾ | 0.43 | 2.06 2 | 0.49 | 2.35 2¼ | 0.55 | 2.64 2½ | 0.61 | 2.93 2¾ | 0.67 | 3.22 3 | 0.73 | 3.5 3¼ | 0.79 | 3.79 3½ | 0.85 | 4.08 3¾ | 0.91 | 4.37 4 | 0.97 | 4.66 4¼ | 1.03 | 4.94 4½ | 1.09 | 5.23 4¾ | 1.15 | 5.52 5 | 1.21 | 5.81 ----------------+------------+------------ Bulk-percentage to be read from graduation on the side of the tube. * * * * * {63} Nine-tenths of the sulphuric acid is in combination with various mineral substances (mineral or preformed sulphates). One-tenth is in combination with certain aromatic substances, mostly products of albuminous putrefaction in the intestine (conjugate sulphates). Among these aromatic substances are indol, phenol, and skatol. By far the most important of the conjugate sulphates and representative of the group is potassium indoxyl sulphate. Potassium indoxyl sulphate, or indican, is derived from indol. Indol is absorbed and oxidized into indoxyl, which combines with potassium and sulphuric acid and is thus excreted. Under normal conditions the amount in the urine is small. It is increased by a meat diet. Pathologically, an increase of indican always indicates abnormal albuminous putrefaction somewhere in the body. It is noted in: (_a_) _Diseases of the Small Intestine_.--This is by far the most common source. Intestinal obstruction gives the largest amounts of indican. It is also much increased in intestinal indigestion--so-called "biliousness"; in inflammations, especially in cholera and typhoid fever; and in paralysis of peristalsis such as occurs in peritonitis. Simple constipation and diseases of the _large_ intestine alone do not increase the amount of indican. (_b_) _Diseases of the stomach_ associated with deficient hydrochloric acid, as chronic gastritis and gastric cancer. Diminished hydrochloric acid favors intestinal putrefaction.