A number of chemicals that could dissolve the organic part of the dental calculus or its inorganic salts were testedin vitroas possible anti‐calculus agents. Several of them were tried in combination. The effect was studied for five and ten minutes on finely meshed calculus, dentine and enamel.None of the chemicals tested, either alone or in combination with another chemical, had a selective effect on calculus. On the basis of total weight, dentine was often dissolved to a greater extent than calculus, although the percentage of total phosphorus dissolved was greatest for calculus. Organic solvents always showed a low dissolution effect. However, Ascoxal at pH 4.5–5 showed a much greater effect on calculus than on dentine and ena