1. A PROCESS FOR THE RECOVERY OF CHEMICAL SUBSTANCES FROM VISCOSE RAYON SPINNING BATHS CONTAINED SULPHURIC ACID, SODIUM SULPHATE AND ZINC SULPHATE, SAID ZINC SULPHATE BEING PRESENT IN AN AMOUNT GREATER THAN 0 AND LESS THAN ABOUT 2 PER CENT, WHICH COMPRISES REMOVING WATER BY EVAPORATION FROM THE SPINNING BATH LIQUOR UNTIL THE TOTAL PROPORTION BY WEIGHT OF SODIUM SULPHATE CALCULATED AS NA2SO4 PRESENT IN THE LIQUOR AND AS PRECIPITATED CRYSTALS EXCEEDS 30 PER CENT OF THE WEIGHT OF THE CONCENTRATED LIQUOR AND ADJUSTING THE SULPHURIC ACID CONTENT OF THE CONCENTRATED LIQUOR UNTIL IT IS IN EXCESS OF 17 PER CENT BY WEIGHT OF THE WEIGHT OF THE CONCENTRATED LIQUOR, COOLING THE CONCENTRATED LIQUOR CONTAINING MORE THAN 30 PER CENT NA2SO4 AND MORE THAN 17 PER CENT H2SO4 TO BELOW 32* CENTIGRADE WHEREBY COMPLEX SALTS OF SODIUM SULPHATE, SULPHURIC ACID AND ZINC SULPHATE ARE PRECIPITATED, SEPARATING THE PRECIPITATED CRYSTALS FROM THE MOTHER LIQUOR AND DECOMPOSING THE PRECIPITATED CRYSTALS TO THEIR CONSTITUENT SALTS BY FIRST REDUCING THE ACID CONTENT OF THE CRYSTALS TO 17 PER CENT BY WEIGHT BY WASHING THEM AT A TEMPERATURE BELOW 32* CENTIGRADE WITH AQUEOUS SATURATED SODIUM SULPHATE LIQUORS CONTAINING SULPHURIC ACID IN A CONCENTRATION OF AT LEAST 17 PER CENT BY WEIGHT, AND THEN WASHING THE CRYSTALS AT A TEMPERATURE ABOVE 32* CENTIGRADE WITH AQUEOUS SATURATED SODIUM SULPHATE LIQUORS CONTAINING SULPHURIC ACID IN A CONCENTRATION GREATER THAN 0 PER CENT BUT BELOW 17 PER CENT BY WEIGHT WHEREBY THE COMPLEX SODIUM SULPHATES PRESENT IN THE CRYSTALS ARE CONVERTED INTO ANHYDROUS SODIUM SULPHATE SUBSTANTIALLY FREE FROM ACID AND ZINC SALTS.