recovered tar are separated naphthalene, toluene and anthracene from which are derived the brilliant coal-tar colors and many synthetic medicinal compounds, also disinfectants and preservatives like carbolic and benzoic acids. In Germany the coal coked so that the by-products could be recovered was 30 per cent, in 1900; 82 per cent, in 1909.
Our chemists are devising means to prevent the contamination of the atmosphere by industrial wastes. Witness the Sulphur, Copper and Iron Company at Ducktown, Tenn, whose blast furnace gases contain a high percentage of sulphur dioxide because of the abundance of sulphur in the ores. Instead of, as formerly, allowing this to escape to poison the surrounding vegetation it is caught and converted into sulphuric acid. One hundred and sixty tons are produced daily, of high purity; a waste product has been converted into an article of commerce for which there is a constant demand.
In agriculture the general outlook is highly encouraging. True, much time will pass before the agricultural chemist is estimated at his real value, but even now the farmer is making use of his assistance and asking for his aid with increasing frequency. He is learning that the old "rule-of-thumb" methods are unprofitable, and when he is convinced that science can more abundantly fill his purse, the end that we desire is in sight. It is within the remembrance of most of us what a change has taken place in Iowa, within the past fifteen or twenty years with respect to fertilizers—the putting back into the bosom of mother nature the nourishing elements of which our crops have deprived her. Fortunately our farms are still exceptionally fertile and by scientific treatment we of Iowa may not be reduced to that dependence upon artificial plant food which is so painfully noticeable in New England and other eastern states. But our pride in our soil should not lead us to overlook our imperfections. When we know that our average wheat crop is, for the country, only twelve to fifteen bushels to the acre, that of England, the Netherlands and Denmark over twice that and that on some of our experimental farms it runs up to seventy to eighty bushels, it should make us pause for serious reflection. On the other hand, if, as we are told, the average crop of the Romans was but four to five bushels we can take courage and strive for better results.
I have spoken of new means of getting nitrogen, one of the three plant nutrients most apt to be deficient. A second, potassium, occurs abundantly in feldspars in a comparatively insoluble form. Recent experiments by chemists, however, indicate that through very fine grinding the door is unlocked which will set it free in a form which the plant can assimilate. For the third nutrient, phosphoric acid, we must probably depend upon re-using that taken up by the plant or upon undeveloped deposits. Happily, we have such ones. Announcement has just been made by geologists of large phosphate beds in several of our western