[On Oxygen, Chlorine, Iodine, Fluorine:] The most important division of ponderable substances seems to be that which represents their electrical energies or their respective inherent states. When the poles of a voltaic apparatus are introduced into a mixture of the simple substances, it is found that four of them go to the positive, while the rest evince their state by passing to the negative pole. As this division coincides with one resulting from a consideration of their most important properties, it is that which I shall adopt as the first.

[Professor W.L. Bragg asserts that] In sodium chloride there appear to be no molecules represented by NaCl. The equality in number of sodium and chlorine atoms is arrived at by a chess-board pattern of these atoms; it is a result of geometry and not of a pairing-off of the atoms.

[The popular impression about some chemists is that] the aquafortis and the chlorine of the laboratories have as effectually bleached the poetry out of them, as they destroy the colours of tissues exposed to their action.

[To elucidate using models] the different combining powers in elementary atoms, I … select my illustrations from that most delightful of games, croquet. Let the croquet balls represent our atoms, and let us distinguish the atoms of different elements by different colours. The white balls are hydrogen, the green ones chlorine atoms; the atoms of fiery oxygen are red, those of nitrogen, blue; the carbon atoms, lastly, are naturally represented by black balls. But we have, in addition, exhibit the different combining powers of these atoms … by screwing into the balls a number of metallic arms (tubes and pins), which correspond respectively to the combining powers of the atoms represented … to join the balls … in imitation of the atomic edifices represented.

Chlorine is a deadly poison gas employed on European battlefields in World War I. Sodium is a corrosive metal which burns upon contact with water. Together they make a placid and unpoisonous material, table salt. Why each of these substances has the properties it does is a subject called chemistry.

Chlorine is a poisonous gas. In case I should fall over unconscious in the following demonstration involving chlorine, please pick me up and carry me into the open air. Should this happen, the lecture for the day will be concluded.

From common salt are obtained chemically as primary derivatives chlorine—both a war gas and a means of purifying water; and 'caustic soda.' … [O]n the chlorine side there is obtained chloride of lime, (a bleaching powder and a disinfectant), chloroform (an anesthetic), phosgene (a frightful ware gas), chloroacetophenone (another war gas), and an indigo and a yellow dye. [O]n the soda side we get metallic sodium, from which are derived sodium cyanide (a disinfectant), two medicines with [long] names, another war gas, and a beautiful violet dye. Thus, from a healthful, preservative condiment come things useful and hurtful—according to the intent or purpose.

I have never seen a food writer mention this, but all shrimp imported into the United States must first be washed in chlorine bleach to kill bugs. What this does for the taste, I do not know, but I think we should be told.

I was an impostor, the worthy associate of a brigand, &c., &c., and all this for an atom of chlorine put in the place of an atom of hydrogen, for the simple correction of a chemical formula!

In one department of his [Joseph Black’s] lecture he exceeded any I have ever known, the neatness and unvarying success with which all the manipulations of his experiments were performed. His correct eye and steady hand contributed to the one; his admirable precautions, foreseeing and providing for every emergency, secured the other. I have seen him pour boiling water or boiling acid from a vessel that had no spout into a tube, holding it at such a distance as made the stream’s diameter small, and so vertical that not a drop was spilt. While he poured he would mention this adaptation of the height to the diameter as a necessary condition of success. I have seen him mix two substances in a receiver into which a gas, as chlorine, had been introduced, the effect of the combustion being perhaps to produce a compound inflammable in its nascent state, and the mixture being effected by drawing some string or wire working through the receiver's sides in an air-tight socket. The long table on which the different processes had been carried on was as clean at the end of the lecture as it had been before the apparatus was planted upon it. Not a drop of liquid, not a grain of dust remained.

In organic chemistry there exist certain types which are conserved even when, in place of hydrogen, equal volumes of chlorine, of bromine, etc. are introduced.

IODINE
It was Courtois discover'd Iodine
(In the commencement of this century),
Which, with its sisters, bromine and chlorine,
Enjoys a common parentage - the sea;
Although sometimes 'tis found, with other things,
In minerals and many saline springs.

But yet the quantity is so minute
In the great ocean, that a chemist might,
With sensibilities the most acute,
Have never brought this element to light,
Had he not thought it were as well to try
Where ocean's treasures concentrated lie.

And Courtois found that several plants marine,
Sponges, et cetera, exercise the art
Of drawing from the sea its iodine
In quantities sufficient to impart
Its properties; and he devised a plan
Of bringing it before us - clever man!

It is more important to know the properties of chlorine than the improprieties of Claudius!

There's antimony, arsenic, aluminium, selenium,
And hydrogen and oxygen and nitrogen and rhenium,
And nickel, neodymium, neptunium, germanium,
And iron, americium, ruthenium, uranium,
Europium, zirconium, lutetium, vanadium,
And lanthanum and osmium and astatine and radium,
And gold and protactinium and indium and gallium,
And iodine and thorium and thulium and thallium.
There's yttrium, ytterbium, actinium, rubidium,
And boron, gadolinium, niobium, iridium,
And strontium and silicon and silver and samarium,
And bismuth, bromine, lithium, beryllium and barium.
There's holmium and helium and hafnium and erbium,
And phosphorus and francium and fluorine and terbium,
And manganese and mercury, molybdenum, magnesium,
Dysprosium and scandium and cerium and cesium,
And lead, praseodymium and platinum, plutonium,
Palladium, promethium, potassium, polonium,
And tantalum, technetium, titanium, tellurium,
And cadmium and calcium and chromium and curium.
There's sulfur, californium and fermium, berkelium,
And also mendelevium, einsteinium, nobelium,
And argon, krypton, neon, radon, xenon, zinc and rhodium,
And chlorine, cobalt, carbon, copper, tungsten, tin and sodium.
These are the only ones of which the news has come to Harvard,
And there may be many others, but they haven't been discarvard.
[To the tune of I am the Very Model of a Modern Major General.]

What we call recycling is typically the product losing its quality. Paper gets mixed with other papers, re-chlorinated and contaminated with toxic inks. The fiber length gets shorter…and you end up with gray, fuzzy stuff that doesn't really work for you. That's downcycling. Michael Braungart and I coined the term upcycling, meaning that the product could actually get better as it comes through the system.