On pages 3 and 16, of this volume of the Sci entific American, we published the experiments ci Dr. Jackson, of Boston, with chlo-**"**. \nd fusel oil, and stated, as we believed . '.iHa fact, that he had made a most - .' discovery in finding out the cause of c deaths which had occurred by the use U i'jroforai. The chloroform which had Av? j sed was made oiit of whiskey, which e* .y'"- this oil, instead of being made out of f 'j* alcohol. We now have to state that this nt a MW discovery. On pages 280 and 2Ri, '. "Chambers' Edinburgh Journal," for 1350, there is a paper by Professor Gregory on this very subject, which speaks of the danger arising from making chloroform of the pyroxylin spirtfeptcommerce. He states that this i spirit o t* ifnerce contains impurities of oils, and the c'Aroform made of it'"is extremely dangerous, because the oils mentioned are very deleterious when inspired, causing migraine, sickness, and vomiting. These effects may be i produced by chloroform containing but a small f portion of these oils, the vapor of which F comes in contact with the internal surface of? the lungs. A larger proportion of oils, such as is sometimes tound, may produce very serious results, hence the necessity of perfect purification." These quoted sentences embrace the very discovery asserted to have been made by Dr. Jackson. It is essential thatevery medical man should be enabled to ascertain, readily, whether any given specimen of chloroform be pure. Dr. Gregory presents some very excellent tests for detecting impure and proving pure chloroform, which are so plain that no surgeon nor dentist in our country can be excused, after this, for using any that is impure. One is, pure chloroform has the density of l'500, but as this test is troublesome, depending on temperature and delicate instruments, two other modes are given. The next is to shake the chloroform in a well stoppered (not corked) bottle, along with one-half of its bulk of the oil of vitriol (colorless) ot the density of 1840. If any trace of oils is present, the acid becomes more or less yellow, and when allowed to stand, a darker line appears at the junction of the liquids. When the yellow color appears, after being shaken and standing still for a short time, the chloroform is poured off into another vial, where it is shaken anew, with another and a smaller portion of vitriol. If,.atter a time, this appears colorless, the chloroform may be considered pure, and it only remains to remove the acid from the chloroform. This is easily done by pouring the chloroform into a third dry vial, and shaking it with a little peroxide ot manganese till its smell is quite free from that of sulphurous acid, which is very soon the case; its specific gravity is then l'SOO, and it is perfectly pure. Another test, but a very delicate one, is to allow a little chloroform to evaporate from the palm of the hand; when pure it leaves no smell, but if there be a trace of oils they, being less volatile, remain and present a disagreeable odor. It is very difficult to get chloroform, so pure that it will leave no odor when thus tested ; but no practitioner should use chloroform if it leaves a strong and distinct smell of noxious oils, or if it colors the acid. These tests are easy, and chemists cannot be offended if surgeons refuse to use their impure chloroform, when it is so easy of purification and so dangerous to use. Pure chloroform produces none of the persistent sensations which are caused by the impure. Dr. Gregory has seen a specimen labelled "pure chloroform," which scarcely contained a trace of that liquid, and Dr. Simpson, the discoverer of chloroform, once received a bottle of apparently pure stuff from a maker otgood character, and there was not one of his patients but suffered from its use, until he suspected the cause, tried it and found it to be impure. In " Chambers Journal," lor 1851, page 57, it is stated that it has been administered in Edinburgh 80,000 times without a single accident. We have now a true clue to the cause of death produced, in more than one instance in our country, on persons who had previously inhaled chloroform without the least evil effect.