thus it is possible to produce in a simple manner a highly stable product which is suitable for sale in a solid form as tablets or in the form of a solution contained in an ampoule after the diphosphonic acid reduced metal salt preparation has been added to a pertechnetate solution the resultant complex forms a very effective means for diagnosing bone tumors local disorders in bone metabolism and calciferous tissue tumors the present invention will now be further described by means of the following examples which are not limitative in any manner 57 6 gm 0 2 mol of tetraethyl methylenediphosphonate and 34 4 gm 0 4 mol of methyl acrylate were mixed and 12 to 14 ml of freshly prepared saturated ch 3 ona ch 3 oh solution were added drop by drop under agitation the reaction temperature reached 90 u00b0 c agitation was continued for 2 hours at 90 u00b0 c to 100 u00b0 c after the exothermic reaction had ceased the reaction product was then subject to vacuum fractionation the main fraction of the ester obtained had a boiling point of 210 u00b0 c to 216 u00b0 c 0 09 torr the density n d 20 was 1 4513 the yield was 88 the ester obtained was subsequently saponified by refluxing for a long period of time with concentrated hydrochloric acid and the free acid was separated the yield upon saponification was approximately 86 in accordance with potentiometric titration the diphosphonoalkane dicarboxylic acid of the formula str5 i r u2550 ch 2 ch.