Abstract: A new procedure for preparing the calcium carbide has been described, wherein the CO₂ gas reacts directly with calcium (with a small amount of magnesium), being heated in a stainless steel vessel. This technique of conversion of CO₂ to C₂H₂ is as convenient as Barker's (2). In general its recovery is about 90%.A special electronic circuit was used to discriminate the "cross-talk" between the two photomultipliers, thus reducing the background of the scintillation counter to 5.6 ?0.1 cpm, while the net counting rate of the modern standard is 58 cpm.