A SIMPLE DEVICE FOR WEIBRINB BASES JOHN W. CAITTOM u d ROT I. ORADT The College of W&er, W d e r , Ohlo
AT TIM= the chemint needs to know when a certain predetermined weight of gas has l w n used in an experiment. At othrr times he may wish to know the rate st whirh a gns hns I m n delivered. The n-riters hnve devised a sclreme for accomplishing the above purp w s without encountering the difficulties involved in the use of the usunl flowneter. The drvice mny resemble others in uw, hut no other system with nn electric nlnnn nttnchrd hns come to the nttention of the authors. Plntform "scales" of the type usually found in feed storrs were uml. The capacity wns 310 lb. The usual cylinder of gas was placed on the plntform. An electric circuit with dry cells I?, signal huzzrr A, and knife m i t r h K wns ntt.whed to thr systrm na shown in the accompanying dingrnm. With the knife switch c l o d and the beam in rontnct with the point C the circuit wns closed through the beam nnd the huzzrr would aound. With n tntnl weight of 80 kg. on the plntform this device could i)r adjnsttd so delicntely that n vnrintion of 5 g. would be enough to mnke or brrnk the circuit. For this rrnaon the rylinder wns hnlnncrd roughly with the weight 11' on the lxnm and aupplcmentary braas weights of the u ~ u n llnboratory variety were p l n c d h s i d r the cylindrr on the plntform. The .system
was condderd to be balanced when the circuit was rlosed drfinitrly enough to give regular clicks in the buzmr. To w e the deviw in weighing gas the ~ y s t e mwan first hnlnncd ns d e s c r i l d above, nnd then a predetermined brmq weight (my 100 g.) was added to the hnlnncd plnt,form. This lifted the beam nntl broke the rircuit. After the corresponding amount of gas had been delivered, the circuit would nutomnticnlly close and the buzzer would sound the alarm. T o prevent the beam from making rontnct with the top of the " h m stop" D,thnt portion ~ v n sinsulated. Clean contacts were essential far nccurnte mensurrmenta. Whwe a constant rate of flow was desired, a bubble counter was insrrtrd in the line.
