the physical configurations of benzotriazole

[David Lyga]

Way back in the 60s and 70s, Kodak marketed its 'anti-fog' (Benzotriazole) in a glass bottle and the substance was a tight powder that did not pour too easily. Then, Photographers' Formulary marketed it as 'feathers': very light, fluffy substance whose volume was huge compared to its weight. NOW, Photographers' Formulary (I just bought some) markets it as tiny granules (very easy to pour).

Why these physical modifications over the decades? Heretofore, this was the ONLY chemical that I have never been able to measure by volume and had to find a scale for metric mass. NOW, happily, the granules DO allow such volumetric measurement. (Five mL volume of the granules equates with 3 grams.) Comments? - David Lyga

 

[dE fENDER]

As in the case of many other chemicals , it depends on the preparation and cleaning methods. In case of BTZ typical laboratory method is to recrystallize crude product from benzene. Such chemical should look like small crystals with form of pins or needles. Other cleaning method is vacuum distillation. After vacuum removing and cooling it solidifies and forms a crust, which is broken to prepare granules.
Some differences in physical properties could be explained by different purity, different temperature conditions while crystallization and others.

 

[RattyMouse]

Way back in the 60s and 70s, Kodak marketed its 'anti-fog' (Benzotriazole) in a glass bottle and the substance was a tight powder that did not pour too easily. Then, Photographers' Formulary marketed it as 'feathers': very light, fluffy substance whose volume was huge compared to its weight. NOW, Photographers' Formulary (I just bought some) markets it as tiny granules (very easy to pour).

Why these physical modifications over the decades? Heretofore, this was the ONLY chemical that I have never been able to measure by volume and had to find a scale for metric mass. NOW, happily, the granules DO allow such volumetric measurement. (Five mL volume of the granules equates with 3 grams.) Comments? - David Lyga

Measuring the volume of powders? Never heard of such a thing, despite being an industrial chemist for the past 25 years.

Why use a clearly substandard method of measurement?

 

[Doremus Scudder]

Measuring the volume of powders? ... Why use a clearly substandard method of measurement?

Not wanting to start an argument here, but "powders" and other solids get measured in volumes in lots of contexts (cooking, doing laundry, chlorinating your swimming pool, etc.). For these purposes, measuring solids in volumes (especially if the physical characteristics of the solid are fairly consistent, e.g., laundry powder) is accurate enough.

For some photographic purposes, measuring dry chemicals in volume is also "accurate enough." I mix my wash-aid with a Tablespoon measure for sodium sulfite and a pinch between thumb and forefinger for bisulfite. I have a spoon recipe for soft-working print developer that is quick and easy and works well despite the inherent inaccuracies in spoon-measuring chemicals.

So, "substandard"? It depends on your standards. Measuring more accurately than necessary certainly won't hurt, but when there's a significant time savings resulting from a less-accurate but still adequate measuring method, then there is justification.

Best,

Doremus

 

[David Lyga]

Measuring the volume of powders? Never heard of such a thing, despite being an industrial chemist for the past 25 years.

Why use a clearly substandard method of measurement?

My years and years of measuring: metol, hydroquinone, sodium sulfite, anhy, and many, many other chemicals proves, at least to me, that accuracy was never a concern with volumetric measurement. My development times remain the same despite the theoretical 'encumbrance'. In fact, I will not hesitate to buy a large size of Dektol and simply measure what I want for immediate mixing. True, I do not mix only tiny quantities (error creeps in) but I have found that with these multi-chemical formulas the chances of getting skewed proportions is very minor, indeed. I have had no problems and I think that a statistician would admit that the Standard Deviation thereof would be very low. In life, I do what works, not what I am TOLD will work. - David Lyga

 

[David Lyga]

As in the case of many other chemicals , it depends on the preparation and cleaning methods. In case of BTZ typical laboratory method is to recrystallize crude product from benzene. Such chemical should look like small crystals with form of pins or needles. Other cleaning method is vacuum distillation. After vacuum removing and cooling it solidifies and forms a crust, which is broken to prepare granules.
Some differences in physical properties could be explained by different purity, different temperature conditions while crystallization and others.

Thank you for illuminating for me what is standard knowledge for you. - David Lyga

 

[David Lyga]

Not wanting to start an argument here, but "powders" and other solids get measured in volumes in lots of contexts (cooking, doing laundry, chlorinating your swimming pool, etc.). For these purposes, measuring solids in volumes (especially if the physical characteristics of the solid are fairly consistent, e.g., laundry powder) is accurate enough.

For some photographic purposes, measuring dry chemicals in volume is also "accurate enough." I mix my wash-aid with a Tablespoon measure for sodium sulfite and a pinch between thumb and forefinger for bisulfite. I have a spoon recipe for soft-working print developer that is quick and easy and works well despite the inherent inaccuracies in spoon-measuring chemicals.

So, "substandard"? It depends on your standards. Measuring more accurately than necessary certainly won't hurt, but when there's a significant time savings resulting from a less-accurate but still adequate measuring method, then there is justification.

Best,

Doremus

Thank you Doremus: you have caught reality by the hook and left threatening theories in the dust. Sure, these theories are valid for mass measurement, but common sense is sometimes permitted to invade such inner sanctum. My years of doing this are good enough for my demanding sense of accuracy. But, Doremus, I do not like teaspoons (5mL) or tablespoons (15mL). I prefer a calibrated cylinder which is considerably more accurate (baby feeding section in CVS). - David Lyga

 

[RattyMouse]

Thank you Doremus: you have caught reality by the hook and left threatening theories in the dust. Sure, these theories are valid for mass measurement, but common sense is sometimes permitted to invade such inner sanctum. My years of doing this are good enough for my demanding sense of accuracy. But, Doremus, I do not like teaspoons (5mL) or tablespoons (15mL). I prefer a calibrated cylinder which is considerably more accurate (baby feeding section in CVS). - David Lyga

My reference point is waaay off base here. Clearly the work being done here has.a much lower need for accuracy than what I'm used to as a formulation scientist. It's easy for me to forget that. I've been doing this for just shy of 25 years and have met countless colleagues from all across the globe and none have ever measured solids by volume. None. Of course, our formulations go to the second decimal point, and in some cases, the third. Way beyond what home photography needs are.

 

[avb]

Measuring the volume of powders? Never heard of such a thing, despite being an industrial chemist for the past 25 years.

Why use a clearly substandard method of measurement?

Tap density is used frequently to measure the density of powders in g/mL. This can be reported actually as the density of powders for a certain number of taps of a certain size graduated cylinder. At a certain point the powder does not settle any more. The tap density can be compared to crystallographic density to determine porosity of the powder. There are other powder density measurement as well, such as pellet density (powder is pressed into a pellet at a certain pressure).

 

[Doremus Scudder]

My reference point is waaay off base here. Clearly the work being done here has.a much lower need for accuracy than what I'm used to as a formulation scientist. It's easy for me to forget that. I've been doing this for just shy of 25 years and have met countless colleagues from all across the globe and none have ever measured solids by volume. None. Of course, our formulations go to the second decimal point, and in some cases, the third. Way beyond what home photography needs are.

Ratty,

I think the need for measuring accuracy in a typical darkroom falls somewhere between dosing your washing machine and the ultra-precise measurements a lab such as you are used to working in needs. Some things, such as dry developing agents and stock solutions of many developers need fairly accurate measurement to achieve repeatablility of results. I have a triple-beam chemical balance scale that is accurate at least to 0.1g for weighing out small amounts of things like phenidone and benzotriazole, graduated pipettes and syringes for developer concentrates and a host of graduated cylinders in various sizes. However, for some things, like wash-aid or a down-and-dirty print developer from scratch, I find volume measurements to be precise enough. I only sacrifice precision when 1) it makes no appreciable difference in the end result and 2) it significantly streamlines my workflow (e.g., saves time). We shouldn't develop sloppy work habits and not accurately weight out or measure things that need precision. But, we can recognize things that need less precision and optimize our procedures by using faster, albeit less-precise, means of measuring. And, we should know the difference between these two.

Best,

Doremus

 

[RattyMouse]

Ratty,

I think the need for measuring accuracy in a typical darkroom falls somewhere between dosing your washing machine and the ultra-precise measurements a lab such as you are used to working in needs.

Well said.

 

[MattKing]

Adding to what Doremus has posted, I find it really enhances my understanding of what I am doing when I understand the relative needs for precision.
Some things work well if you use kitchen measurements with them. Other things require much more precision. While other things are sufficiently accurate using pinches and handfuls and the like.
This is extremely advantageous for those of us who don't have easy access to precision equipment or tools.

 

[David Lyga]

My reference point is waaay off base here. Clearly the work being done here has.a much lower need for accuracy than what I'm used to as a formulation scientist. It's easy for me to forget that. I've been doing this for just shy of 25 years and have met countless colleagues from all across the globe and none have ever measured solids by volume. None. Of course, our formulations go to the second decimal point, and in some cases, the third. Way beyond what home photography needs are.

I do, however, have one nagging question that has rarely been attempted: Do any of the chemical powders ever acquire a tiny bit of water from the air, thus making their respective masses a bit higher? Is metric mass measurement really that absolute and definitive? - David Lyga

 

[RattyMouse]

I do, however, have one nagging question that has rarely been attempted: Do any of the chemical powders ever acquire a tiny bit of water from the air, thus making their respective masses a bit higher? Is metric mass measurement really that absolute and definitive? - David Lyga

Absolutely. That happens quite a lot. However, we formulate with these raw materials that have been fully hydrated and so this already accounted for by the time the formula hits production.

Anhydrous materials have to be handled in a completely different way to remain water free. That's not an important criteria in my industry.

 

[Gerald C Koch]

In organic synthesis the product usually needs to be purified. How this is done determines the density of the final product. The denser product is crystallized from a solvent while the fluffier one is purified by sublimation.

 

[Gerald C Koch]

I do, however, have one nagging question that has rarely been attempted: Do any of the chemical powders ever acquire a tiny bit of water from the air, thus making their respective masses a bit higher? Is metric mass measurement really that absolute and definitive? - David Lyga

BZT is not hygroscopic.