This distillation of sulphuric acid with sea-salt, which yielded spirit of salt, or as it is now called hydrochloric acid, was probably Glauber’s principal contribution to the development of chemistry. He observed the gas given off from the salt, and it is a wonder that with his acuteness he did not isolate and describe the element chlorine. He called it the spirit of rectified salt, and described it as a spirit of the colour of fire, which passed into the receiver, and which would dissolve metals and most minerals. He noted that if digested with dephlegmated (concentrated) spirit of wine his spirit of salt formed a layer of oily substance, which was the oil of wine, “an excellent cordial and very agreeable.” He distilled ammonia from bones, and showed how to make sal ammoniac by the addition of sea salt. His sulphate of ammonia, now so largely used as a fertiliser and in the production of other ammonia salts, was known for a long time as “Sal ammoniacum secretum Glauberi.” He made sulphate of copper, and his investigation of the acetum lignorum, now called pyroligneous acid, though he did not claim to have discovered this substance, was of the greatest value. He produced artificial gems, made chlorides of arsenic and zinc, and added considerably to the chemistry of wine and spirit-making. Glauber worked at many subjects for manufacturers, and sold his secrets in many cases. His enemies asserted that he sold the same secret several times, and that he not unfrequently sold secrets which would not work. It is impossible now to test the truth of these accusations. Probably some of the allegations made against him were due to the fact that those who bought his processes were not as skilful as he was. One secret which he claimed to have discovered he would neither sell nor publish. It was that of the Alkahest, or universal solvent. To make this known might, he feared, “encourage the luxury, pride, and godlessness of poor humanity.” Oliver Cromwell wrote in an old volume of Glauber’s Alchemy: “This Glauber is an errant knave. I doe bethinke me he speaketh of wonders which cannot be accomplished; but it is lawful for man too the endeavour.”