Abstract: Compounds of the general formula: ##STR1## (where R is a group --CH(CH.sub.2 OH).sub.2 or --CH.sub.2 CH(OH)CH.sub.2 OH and A is a group --CH.sub.2 CH(OH)CH.sub.2 -- or --CH.sub.2 CH(OH)CH(OH)CH.sub.2 --) possess a package of favourable parameters which render them of particular use not only in all forms of intravascular visualisation but also in myelography.The compounds are prepared by reaction of an appropriate 5-acetylamino-N,N'-bis(hydroxypropyl)-2,4,6-triiodoisophthalamide with an agent effective to introduce the appropriate hydroxyalkylene group such as for example epichlorohydrin or 1,4-dichloro-2,3-dihydroxybutane.

Abstract: Compounds of the general formula: ##STR1## (wherein R represents --CH(CH.sub.2 OH).sub.2 or --CH.sub.2 CH(OH)CH.sub.2 OH) possess a package of favorable parameters which render them of particular use not only in all forms of intravascular visualization but also in myelography.The compounds are prepared by reaction of the corresponding 5-monoacetylamino compound with one or more reagents effective to introduce the 2-hydroxy-3-methoxypropyl group.

Abstract: The invention provides a process for the preparation of 3-acetamido-5-amino-2,4,6-triiodobenzoic acid substantially free from diiodinated material, in which 3-acetamido-5-aminobenzoic acid or a salt thereof is gradually introduced into an aqueous acid system which contains an excess of iodine chloride (ICl) in a stabilized form. In particular, the gradual introduction of 3-acetamido-5-aminobenzoic acid may be achieved by using 3,5-diacetamidobenzoic acid as starting material, the acid medium effecting hydrolysis of one acetamido group and the excess iodinating reagent reacting selectively at such a rapid rate that the desired triiodinated product is formed and precipitated without further hydrolysis or premature precipitation of unwanted diiodinated products.