Use Thermo Scientific™ Orion™ AQUAfast Digestion Tubes, Reaction Tubes and Liquid Reagents with Orion™ AQUAfast colorimeters and Thermo Scientific™ Orion™ AquaMate Vis and UV-Vis spectrophotometers. Digestion and reaction tubes contain the precise amount of reagent, are made of special optical glass and fit the Orion™ AQUAfast COD165 thermoreactor. Digestion tubes measure COD, total nitrogen and total phosphate. Reaction tubes measure ammonia, nitrate and phosphate. Liquid reagents mix quickly and easily in solution and measure fluoride (SPADN), hydrazine and pH.