# Percentages and mgm/ml

Discussion in 'B&W: Film, Paper, Chemistry' started by Murray Kelly, Jan 26, 2008.

1. ### Murray KellyMember

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I have read a lot of threads here that describe amounts of a chemical required to make a working solution (or stock) using a concentrate that often requires mental gymnastics to work out how much of your concentrate are needed to make up a 'brew'.

A trick I learned over 40 y ago in my line of business (anesthesiology) was a quck way to work out how much of the agent, in our case an amount of say Phenidone, you would add of a percentage solution you have to deliver the milligrams you want in the mix.

The 'rule de thumb' is you mentally multiply the percentage by ten and call it mg/ml. E.G. a 1% (1 gram in 100ml of glycol) has (1 x 10) mgm / ml of phenidone. 10mgm.

A 10% solution has 10 x 10 = 100 mgm/ml of the agent.

A 2.5% solution has 2.5 x 10 = 25 mgm/ml of phenidone.

And so it goes.

If this is a puzzle to you, forget I said it!

It can speed up ad hoc mixing of developers etc. if you remember the multiply by ten 'rule'

Hope this is of some help to hombrewers.

Murray
Brisbane, Oz.

2. ### MikeSebMember

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Greetings to a fellow gas-passer, Murray. Now if you can only help me figure out how to do those copper-kettle gas-flow calculations.... Learned it for board exams (sorta--hoped to bluff through without having to answer a question) and forgot it the next day.

I like to say that my brain does active transport--it pushes knowledge out from my skull against a concentration gradient!

3. ### Ian GrantSubscriber

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Mike, don't worry Murray's going to translate everything about percentages first into US ounces, lbs, gallons etc, then he'll have time for your calculations.

Ian

4. ### Murray KellyMember

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It often seems like the brain is like a sponge. Once it's full, you have to squeeze a bit out to get something more in! :-(

I never had to use a copper kettle (thank the Good Lord) - any vaporisers were calibrated in % and of recent years that holds good for really low gas flows. I am a < 1l /min man myself. Without the gas analyser I'd be back in the 70's and flying by the seat of my pants. It worked, tho. Ever used a vaporiser in circuit? My record was 8ml/h of halo/hr. Important if you were paying for the stuff yourself.

No, I just thought the info I gave was useful insofaras it saves a lot of mental agony trying to equate just how much of the stock (%) I need to use to get the desired amount of agent into a formula I read on the 'net.

Murray (dope peddler)
Brisbane, Oz

5. ### Murray KellyMember

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Ian, Percentages are percentages.

Did you know that the USofA went metric in 1975? Not the citizens but the official bodies? My Camaro is all metric. Another Ripley. Believe it or not.

Murray
Brisbane, Oz

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Hi Murray!

Murray

7. ### Murray KellyMember

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Wot!? Another Murray? I often wonder where my poor old Mum ever got that name from in 1936? She was a Geordie, so the border wasn't too far away.

Murray
Brisbane, Oz

8. ### MurrayMinchinMembership CouncilCouncil

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You, me, and Murray@uptowngallery makes three

My dads name is Bill (William) and his second name is Humphrey. Since he had already nabbed William that left me with Humphrey...until I got my moms maiden name, for which I'm eternally grateful!!!!!

Murray

9. ### Murray@uptowngalleryMember

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I didn't run into any other Murray's until I was about 30..and I really can't remember if I ever met them in person...just on the phone, then in later years on the Web.

I had a class in 1976 where they taught us SI units. I learned the exotic style of eliminating radix characters (period vs. comma) for large numbers and using blank spaces. I wonder if I was the only person to learn that because it freaks some people out.

Not needed for developer luckily.

Hey, Murray, at first I thought you were implying phenidone was used in your line of work, then I read it again.

I certainly prefer metric for camera work, weighing chemicals and any small measurements for which the alternative is using a measuring tape with fractions to be misread.

Murray

10. ### Murray@uptowngalleryMember

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My mother had a cousin Mortimer...I'm glad I didn't end up Mortimer@uptowngallery. I'd have had to change my name to something more popular like Cornelius, Rufus or maybe just Spot. Works well for dogs.

11. ### Murray KellyMember

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HeHeHe. We all get this about our name. In New Zealand (my origin) it is quite common. I didn't meet another Murray until I was abt. 10 yo or so and we both sorta stood off and looked at one another in dumb silence. Quite appropriate some would say. We never said a word.

Uptown - you lost me - I am a simple physician. Well - not so simple but quite ornery. Math was never my strong point so I really latched on to the 1 x 10 percentage to mgm/ml rule. If I find it useful I'm sure others would, too.

These days clan names and such (Murray, Kelly, Cameron, Frazer etc etc ) are used as first names to the confusion of scribes. As in, 'Is that your first name or your second?' Duh.

Murray
Brisbane, Oz

12. ### Murray KellyMember

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Gotta go - it's 20 to 3 am. Will look for any appreciative replies to the OP or just go bury my head. Everyone knew that about percentages!

73 and take care
Murray
Brisbane, Oz.

13. ### MurrayMinchinMembership CouncilCouncil

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Weird. My best friends name while growing up was Murray, and there were two other Murray's in our grade at high school.

Murray (Also known as Murr)

14. ### Murray KellyMember

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Before I go, the Aussies are notorious for shortening names.
Garry Is Gazza. Larry is Lazza. Murray is Muzza. I even answer to that!

Good night!
M

15. ### NeandermanMember

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Well, there ya go. Now the cat's out of the bag! It's just a good thing Ronald Reagan's not alive to hear you say that...

Ed

16. ### Murray KellyMember

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Yes, Australia did about the same time. Our GovCo went one step further and actually banned the importation of imperial measure instruments including rulers.
They were really serious about going metric. Of course a few years later they relaxed the ban, but by then we were all thoroughly 'metricated'.
My friend in the US bemoans how hard it is to get metric bolts for his Chevvy.

Murray
Brisbane.Oz

17. ### Kirk KeyesMember

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OK - I have to put this link in - Aussies, Cameros, pre-1975. I immediately think of Frank Gardner, owner of the Holden Performance Driving Centre near Norwell, south of Brisbane, Australia - he's twice winner of the British Saloon Car Championship, the European Formula 5000 Champion, runner up awards winner in the European Formula 2 and Touring Car Championship as well as British Champion Racing Driver in 1972, and former Formula One driver. Here's a really nice bit of film of him driving the 550 bhp 1973 Castrol Camero one lap around Oulton Park:

18. ### Kirk KeyesMember

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By the way, the title of this thread is confusing as it does not follow proper SI appreviations for units. Is should be:
"Percentages and mg/ml" as "g" is the correct unit for gram, not "gm".

19. ### Murray KellyMember

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Thanks for that Kirk. I am used to writing mgm to distinguish milligrams from gm which would be interpreted as grams by the pharmacist. The clearer the written instuction the less likely error can creep in. Micrograms is a point of contention as it is written as ugm with the 'u' correctly written as a 'myu' in greek style with a long tail. We are encouraged to write the whole word. I suppose 'ug' would be better but perhaps more confusing than ever. Haven't used 'gr' in years - grains went out with metrification.

I am sorry if I have caused any confusion. I only hope the 'trick' described can be useful to homebrewers! That was my intention.

I'm not sure a lot of folk here would confuse mgm as opposed to mg but it's probably as well to point it out. I see a lot of formulae with a top case 'L' for litres which as you know, is wrong. It does help remove confusion that it is not a '1' should one put the correct 'l' however.

Murray
Brisbane, Oz

20. ### Murray KellyMember

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Oh and Kirk, thanks for the link to Frank Gardner and his 'CamAro'. A common mistake like mgm? Mine is 4th Gen and much more refined for straight street use. I've done less than 50K in the 12+ years I've had it. Converting the steering left to right was really something

I'd be loath to go thru that again.

Murray
Brisbane, Oz

21. ### Kirk KeyesMember

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Yeah, sorry on the name there. I'm not really an American Muscle Car guy. More into Lotuses (Loti?). Speaking of which, my dad owns a car that Frank Gardner drove in 1965 - a Lotus 30 sports racing car. Here's a photo of Frank driving my dad's car at the 1965 Austrian Grand Prix.

http://www.lotus30.com/ImageGallery/Willment/Willment 9.html

The chassis of the car broke midway thought the race and Frank managed to keep the car running and even finished in 3rd place! Frank found it difficult to look anyone straight in the eyes for a week (he said he felt like Eddie Cantor, a singer with the Ziegfeld Follies who was known for his 'banjo eyes') due to the vibration from the Lotus 30 breaking its chassis. He was certainly a driver's driver.

Interesting info about the pharmacy business. You certainly do need to keep very good track of units for that!