Thursday, February 15, 2007

Horse Latitudes.

Just an absolutely brilliant poem:
Horse Latitudes

When the still sea conspires an armor
And her sullen and aborted
Currents breed tiny monsters
True sailing is dead
Awkward instant
And the first animal is jettisoned
Legs furiously pumping
Their stiff green gallop
And heads bob up
In mute nostril agony
Carefully refined
And sealed over

Jim Morrison (The Doors, album Strange Days).
P.S. Horse latitudes are calm waters between 30° and 35° latitude. The story goes that stranded ships traveling to the New World would jettison horses overboard to save water.

Wednesday, February 14, 2007

The stangest flame (ozone-oxygen).

Searching for the ozone flames information, I found the strangest flame ever: pure ozone-oxygen (Streng A.G.; Grosse A.V. The pure ozone to oxygen flame. JACS 1957, 79(6), 1517-1518). Quote:

By using pure ozone, containing less than a few parts per million of organic impurities, as described originally by C. E. Thorp we have been able to burn ozone-oxygen mixtures to oxygen in the entire range from 17-100 mole % 03. The all-Pyrex glass apparatus was extremely simple; it consisted of a narrow glass gasholder, from which any desired mixture of 03-02 or pure 03 could be delivered at any predetermined rate, by simple displacement with water. From the gasholder the gas mixture went to a Pyrex glass, quartz, or aluminum tip. Stopcocks greased with CnF2n+2 or Kel-F, were used. The burning velocities were determined by the standard schlieren method. In the range of 17 to about 50 mole % 03 , the flame cannot be observed visually, but can be seen very easily on the screen of the schlieren apparatus. The flame is visible above this range. Pure 100% ozone burns with a faint, non-luminous flame, blue in color, with a typical pink cast. The experimental burning velocities, at 298°K. and 1.0 atm. pressure, are shown in Fig. 1.
The ozone flame is of particular theoretical interest since it is the simplest flame imaginable. Outside of the “fuel” O3 and the “product of combustion” 02 , the only possible intermediates are oxygen atoms.

The hotter chemical flame (cyanogen-ozone).

A quick search revealed an interesting paper dealing with premixed cyanogen-ozone flames (Streng A.G.; Grosse A.V. The premixed ozone-cyanogen flame. JACS 1957, 79(20), 5583-5583). They did some pretty extreme experiments establishing stability of cyanogen-ozone mixtures:

It was first established, in static experiments, that cyanogen and pure ozone can be mixed and stored for a considerable time without reaction. Thus the mixture 3(CN)2 + 403 was kept in a 100-cc. Pyrex vessel, at 1000 mm. at 0'C for 2.0 hours with no noticeable change in pressure; after this time cyanogen was frozen out at -78", the 03 pumped off and the volumes of the separated gases were found to be essentially equal to their original volumes. Identical results were obtained with the mixture 3(CN)2 + 203.
That is a brave chemistry, that's for sure. Both ozone and cyanogen are extremely toxic, and pure ozone is unstable and readily decomposes explosively. Mixing these things together and warming them up, monitoring the pressure, that is something.

And the description of the flames and temperatures (in Kelvin):

The hottest (?) chemical flame (cyanogen-oxygen).

I just stumbled on an old paper (Conway J.B.; Grosse A.V. The Cyanogen-Oxygen Flame under Pressure. JACS 1958, 80(12), 2972-2976) where cyanogen-oxygen flames were studied. That seems like a pretty suicidal chemistry (cyanogen is extremely toxic). It's interesting that a lot of people studied different aspects of these flames (and mixtures). The paper calls cyanogen-oxygen flame "one of the hottest chemical flames", with its measured temperature being 4367C°. I wonder what is hotter, something like cyanogen-ozone or cyanogen-fluorine flame?

Wednesday, February 7, 2007

Welding copper.

It's been on a busier side during the last few weeks, but I finally got some time to post something new. We had to do some autoclave-kind experiments, but in a much faster and simpler way. So, the ampules provided the solution, once again. Due to very harsh target conditions, my favorite material, glass, had to give way to copper. First, 1/4'' inch copper tube was flattened:Then came the welding itself. Welding torch was used, fed with natural gas/oxygen. You can see the inner cone very well on this photo. The hottest part of the flame is just over the tip of this inner blue cone, and that's what does the welding. It is interesting to note that the inside of the cone is pretty cold (the coldest part of the flame).In a few seconds, copper melts and even starts burning a little, giving the sparks and this green flame: And the seal is done:Here is an ampule after the experiment, you can definitely see the difference:
It's a lot simpler and faster than autoclave, that's for sure.