CHEMIST, one who, for pleasure or profit, concerns himself with the acquisition of information relating to the composition of bodies and the changes of composition which they undergo. The chemist traces his evolution from the Greek philosophers, who speculated without experiment as to the constitution of mat ter, through the mediaeval alchemists, who experimented with little logic, in the hope of transmuting one element into another. Dur ing the middle ages another sect, the iatro-chemists, also existed, who carried out experiments which were to make chemistry more useful to medicine. Many types of chemists exist, classed usually according to the kind of matter or the kind of change with which they are most concerned. When the individual applies his informa tion to the production, manufacture or commercial use of com modities. he is customarily considered a chemical engineer.