In 1912 Pullen[191] reported that he had prepared two specimens of iodine ointment according to the British Pharmacopeia, one being from new lard and the other from a specimen of lard at least 2 years old. Assays for free iodine were carried out immediately after the preparations were made, and at intervals afterward up to four months. The following values were found:
| Sample I | Sample II | |
| Ointment from new lard, per cent. | Ointment from old lard, per cent. | |
| Iodine introduced | 4.0 | 4.0 |
| Iodine found immediately after making | 3.95 | 3.38 |
| Iodine found after twenty-four hours | 3.30 | 3.15 |
| Iodine found on the third day | 3.18 | 2.62 |
| Iodine found on the seventh day | 3.15 | 2.46 |
| Iodine found on the fourteenth day | 3.00 | 2.45 |
| Iodine found after one month | 3.00 | 2.39 |
| Iodine found after two months | 2.90 | 2.31 |
| Iodine found after four months | 2.92 | 2.26 |
Pullen found that the loss in free iodine could be accounted for by the iodine which had gone into combination with the fats of the ointment base.
Pullen also found that if the potassium iodide and glycerin were omitted in the preparation of the ointment, the loss in free iodine was very rapid, the preparation containing practically no free iodine (only 1⁄20) after a few hours. He concludes that the use of potassium iodide and glycerin is necessary for the preservation of the ointment. He obtained specimens of iodine ointment in drug stores, and assayed them for free iodine. It is to be presumed that the ages of the several specimens were not known. The results are found in the following table:
| Specimen No. 1 | 2.74 per cent. |
| Specimen No. 2 | 2.85 per cent. |
| Specimen No. 3 | 2.62 per cent. |
| Specimen No. 4 | 2.48 per cent. |
| Specimen No. 5 | 2.53 per cent. |
| Specimen No. 6 | 2.79 per cent. |
Fried[192] prepared iodine ointment according to the U. S. P. VIII formula, and assayed it at intervals. His results are tabulated herewith:
| Per cent. | |
| Iodine introduced | 4.00 |
| Iodine found immediately after making | 3.89 |
| Iodine found one hour after making | 3.51 |
| Iodine found one day after making | 3.48 |
| Iodine found five days after making | 3.06 |
| Iodine found ten days after making | 2.84 |
| Iodine found thirty days after making | 2.81 |
| Iodine found ninety days after making | 2.81 |
| Iodine found eight months after making | 2.81 |
Iodine ointment has been official in the U. S. Pharmacopeia since 1870. Briefly, the method now used for making the preparation is as follows:
Four gm. of iodine, 4 gm. of potassium iodide and 12 gm. of glycerin are weighed into a tared mortar and the mixture triturated until the iodine and potassium iodide are dissolved and a dark, reddish-brown, syrupy liquid is produced. Eighty gm. of benzoinated lard are then added in small portions and with trituration after each addition. The mass is then triturated until of uniform consistence.[193]