Crystals of laquinimod sodium and improved process for the manufacture thereof

A mixture of crystalline laquinimod sodium particles, wherein 1) (i) 90% or more of the total amount by volume of the laquinimod sodium particles have a size of 40 microns or less or (ii) 50% or more of the total amount by volume of the laquinimod sodium particles have a size of 15 microns or less, or 2) (i) 90% or more of the total amount by volume of the laquinimod sodium particles have a size of less than 40 microns or (ii) 50% or more of the total amount by volume of the laquinimod sodium particles have a size of less than 15 microns, and wherein:

• a) the mixture has a bulk density of 0.2 g/mL to 0.4 g/mL;
• b) the mixture has a tapped density of 0.40 g/mL to 0.7 g/mL;
• c) an amount of heavy metal in the mixture is no more than 0.002% of heavy metal relative to the amount by weight of laquinimod sodium;
• d) an amount of 5-chloro-4-hydroxy-1-methyl-2-oxo-1,2-dihydroquinoline (MCQ) in the mixture is no more than 0.15% relative to the amount of laquinimod sodium as measured by HPLC;
• e) an amount of 5-chloro-4-hydroxy-1-methyl-2-oxo-1,2-dihydroquinoline-3-carboxylic acid (MCQCA) in the mixture is no more than 0.15% relative to the amount of laquinimod sodium as measured by HPLC;
• or
• f) an amount of methyl 5-chloro-4-hydroxy-1-methyl-2-oxo-1,2-dihydroquinoline-3-carboxylate (MCQME) in the mixture is no more than 0.12% relative to the amount of laquinimod sodium as measured by HPLC.