Cloretos (Cl-) nos solos do estado de São Paulo, e sua dosagem

Among the methods purely chemical, used for the determinations of chlorides in the soil, such as gravimetric and volumetric ones and those based on physico-chemical procedures, such as the nefelometric, colorimetric and electrometric ones, we chose on account of being the simplest and most accurate the electro-titrometric method indea-lized by Best (2). It was studied the most reasonable and most perfect technique for the extraction of the chlorides out of the soil and afterwards their titulation. As a means of extraction we chose the distilled water making it percolate through a layer of soil. The ratio between soil and water was 1:4. i. e. 50 g of soil (fine soil) and 200 ml of distilled water. The determinations became thus very accurate and the duration of the electrode of AgCl worked out very well even after 1000 titulations. This will not happen if a rough suspension of soil to make the titulation is used. By this technique it is possible to determine the chlorides without difficulty in 50 soil samples per day. We were able, by this way, to determine chlorides in more than one thousand soil samples of the whole State of S. Paulo. We saw that, in general, the percentage of chlorides is low, ranging between 0.2 and 2 mg of Cl- per 100 grams of soil. In some low lands without circulation of water, we even found 20 mg per 100 grms of soil. So it became evident that we have no cases of soils rich in salts (chlorides) injurious to agriculture. In many cases it became evident that soils were very poor in Ionius Cl- and the addition of chlorides to the manuring was even recommended in order to examine their effects. At the end of our paper we add a great number of analyses showing the percentage of Cl- in the soil, as well as a map of the State with a view to indicate the localization of the samples.