Fluorescent mercury?

[csant]

It suddenly occurred to me that fluorescent lamps (even CFLs) contain mercury vapours – according to Wikipedia CFLs contain up to 3-5mg of mercury, and bigger fluorescent lamps contain even more. Is this enough to be of any use for… mercury development? And is there any way that these vapours can be used for mercury dags? If so, it might be a nice way to re-purpose lamps that have outlive their functioning lifespan…

Never mind if I am talking nonsense – I just started with Becquerel dags, so there is a lot I still need to learn and understand… 🙂

[jgmotamedi]

Getting the mercury out of the bulbs is not going to be an easy task, and 5mg is a tiny amount. You might as well break apart thermometers or look for old mercury switches (my house came complete with two mercury-based thermostats, maybe an ounce of mercury in each). Better yet buy some, it is usually pretty cheap and a pound will last your lifetime.

[csant]

Hi Jason,
thank you very much for your reply. My thinking was along the line: when you heat Hg, how much of it will actually evaporate? I guess that since you say the pound will last a long time, it is only a few mg or g that evaporate? If one can catch the fumes from a bulb (or a few bulbs), it might be enough? One could think of breaking those bulbs inside an air-tight (heated?) box… If that’d work (as in: be enough Hg), this could be a nice alternative way to recylce some Hg which is already out there…

I guess it all comes to to the key question: how many mg are needed for developing one dag?

[jgmotamedi]

I don’t have the answers to your questions, but I can tell you that it isn’t the volume of the mercury that is important per-se but rather the surface area of the mercury. My pot has about two square inches of mercury exposed to the air, with total volume of mercury a little over an ounce. That is about a pound of mercury. Want to do that 5mg at a time?

[photolytic]

 
EQUIVALENT MERCURY PARTIAL PRESSURES vs. TEMPERATURE AND PRESSURE
 

TEMPERATURE
CELSIUS

Mercury
Vapor
Pressure
as mm Hg

Partial
Pressure
@760mm Hg

Partial
Pressure
@150mm Hg

Partial
Pressure
@25mm Hg

30

.0028

.0000037

.0000184

.0001119

50

.0127

.0000167

.0000844

.0005068

80

.0888

.0001168

.0005920

 

 
 
 
 
 
 
 
 
 
 
 
 
 
A liter of air contains 1/22.4 or approx. 0.045 moles of nitrogen and oxygen.
At 80C the partial pressure of mercury vapor under atmospheric pressure is approx 0.089 mmHg/760 or 0.117 millibars.
The partial pressure of mercury vapor is equal to the mole fraction of mercury atoms in the air times the total pressure:     

 pHg = (Total Pressure)x    (Moles of Hg)

                          (Moles of Ox + Nit + Hg)

This corresponds to a concentration of 0.0000053 moles/liter of mercury or approx 1.1 mg of mercury vapor/liter.

It would appear from this that the 2-3mg of mercury in a CFl bulb is more than sufficient to develop at Dag even in a mercury box with a volume of 2 to 3 liters.

However, as jgmotamedi has so wisely pointed out, this is not the whole story. Unless you have a very large number of burned out CFL bulbs, the cost of new bulbs would make them a very expensive source of mercury for the Daguerreotype process.

The CFL bulb also contains a larger quantity of phosphors which would quite likely interfere with the Dag developing process.  

Stick with old mercury switches or thermometers.

 
 
 
 
 
 
 
 
 

[Pobboravsky]

This relates to the amount of mercury needed to develop daguerreotypes.  It comes from Samuel Humphrey’s 1858 American Handbook of the Daguerreotype, pages 41-43.

“There are numerous opinions among operators in regard to the quanitity of mercury necessary for a bath. As regards this, I need only say, similar results occur when two pounds or two ounces are used, but the quantity generally employed is about a quarter of a pound. I am of the opinion that one ounce will answer as well as a larger quantity. I know of no better proof in favor of a small quantity than that presented  in the following incident. Several years since, an operator (Mr. Senter of Auburn N.Y.) of my acquaintance , was requested  to go several miles to take a Daguerreotype portrait of a deceased person.  He packed up his apparatus and proceeded over a rough road for some distance to the house where he was to take the portrait, and arranging his apparatus with all the expedition which the occasion required, after having everything usual order (as was supposed) ,  he proceeded and took some ten or twelve very superior impressions.  They were fine, clear and well developed.  After taking the number ordered, he proceeded to repack his apparatus, and to his surprise, when he took up the bottle he carried the mercury in, he found it still filled, and none in the bath, except only such particles as had adhered to the sides, after dusting and and being jolted for several miles over the rough road. From this it will be seen that a very little mercury will suffice to develop fine proofs.  I saw some of the impressions referred to above, and they were certainly well developed, and very superior specimens of our art”

 

 

 

 

 

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