In the case of manganese oxide, the increase in oxygen absorption on the first day is much more pronounced than is the case with lead oxides. Furthermore, the oxidation of manganese oils seems to be relative to the increase in manganese up to a certain period, when the reverse of this law seems to take place, and beyond a certain definite percentage of manganese, added percentages seem to be of no value. It was furthermore observed that the films dry to a more brittle and harder skin than is the case when lead oxide is used. The oxygen absorption with oils high in manganese has been noticed to be excessive, and the film of oil becomes surface-coated, drying beneath in a very slow manner; a condition that often leads to checking. The critical percentage where the amount of manganese appears to give the greatest efficiency seems to be 0.02%. This critical percentage, as it may be termed, should not be exceeded, and any added amount of manganese has the effect of making the film much more brittle and causes the so-called "burning up" of the paint. The loading of paint with drier and the bad result therefrom may be explained to some extent from the above results. TABLE VI--LINSEED OIL AND MnO_{2} (MANGANESE) DRIER--TEST NO. 1 =========+=========+====+====+====+====+====+====+====+====+==== Per cent.| |0.02|0.05|0.15|0.25|0.35|0.45|0.55|0.70|1.00 MnO_{2} | | | | | | | | | | ---------+---------+----+----+----+----+----+----+----+----+---- |{ 1 day |0.08|0.11|0.16| -- |3.21|3.46|3.27|3.01|2.76 |{ 2 days|0.16|5.88|4.48| -- |3.63|4.01|3.70|3.51|3.18 |{ 3 days|0.21|6.79|4.61| -- |3.83|4.31| -- |3.91| -- |{ 4 days| -- | -- |4.64| -- | -- | -- | -- | -- | -- |{ 5 days|3.01|6.84| -- | -- |4.13|4.68|4.19|3.91|3.99 |{ 6 days|8.00| -- |4.88| -- |4.37| -- |4.51|4.32|4.13 Per |{ 7 days|8.58|6.92|4.90| -- |4.48| -- |4.61|4.52|4.23 cent. |{ 8 days|9.06| -- |5.03| -- |4.55|5.23|4.77|4.62|4.44 gain |{ 9 days| -- | -- |5.12| -- |4.63|5.40|4.94|4.79|4.51 |{ 10 days|9.07|6.89|5.18| -- |4.81|5.47| -- |4.98|4.73 |{ 11 days|9.15|7.03| -- | -- | -- | -- | -- | -- | -- |{ 12 days| -- | -- | -- | -- |4.98| -- |5.45|5.33|5.22 |{ 13 days|9.22|7.17| -- | -- |5.25|6.00|5.60|5.42|5.33 |{ 14 days|9.25|7.18|5.55| -- | -- | -- | -- | -- | -- |{ 20 days| -- |7.21|5.81| -- |5.84|6.70|5.94|5.84|5.77 =========+=========+====+====+====+====+====+====+====+====+==== TABLE VII--LINSEED OIL AND MnO_{2} (MANGANESE) DRIER--TEST NO. 2 (CHECK)