For you analytical chemist types. I’ve been reading the USP monographs and found a viscosity range for a solution. In order to pass, the solution must be between 110 and 147 poises.
Would I consider this a fairly broad range? Are viscosity requirements generally this “loose”?
Can I get a little technical help here?
Is it a solution containing a mixture of various long chain polymers? That can give the solution a pretty wide range of viscosity. 110 Poise is a very high viscosity. Most of the stuff I’m used to measuring is reported in cP to make the numbers more meaningful to the layman.
Hershey’s chocolate syrup runs between 100 and 250 poise.
Viscosity of a solution is often very strongly dependent on the concentration of solutes. For example a 50%w/v aqueous solution of sucrose will have a viscosity of about 10cP, while a 60%w/v solution has a viscosity of nearly 60cP.
The effect is even stronger with some other solutes, e.g Natrasol, where an increase in concentration from 1% to 2% might produce a ten fold change in viscosity.
The upshot of this is that even tight controls on solute concentration can result in a product having a “loose” range of viscosity.
Yes it is a fairly viscous solution. I’m trying to make the point that comercial samples of this particular solution is not easy to accurately characterize. The manufacturers have wide variation from batch to batch. One way I would support this is to show that the USP accepts a wide range of viscosity, simply because it is difficult to manufacture this solution with better control.
Hence I would like to know if this range is “typical” or “big enough to swing a cat through.”
For what its worth the solution is nitrocellulose in organic solvents like acetone or amyl acetate. It can be known as Collodion. I’m personally familiar with this material being difficult to reproducibly manufacture (amount of nitration isn’t so easily controlled), much less get it in solution at a precise concentration. It is usually handled wet, with various and uncontrolled amounts of solvent…the dry stuff being a bit less…friendly.
However, I’d like a citation other than, “I’m personally familiar with…” The USP method seemed like some sort of start.
In my experience, that’s a pretty tight range; look at the product sheet for carbopol resins, and you’ll see that the upper limit for aqueous gels is never less than 130% of the lower limit, and is sometimes more than 5 times the lower limit. Specs for high-viscosity fluids like silicone are similar, except when supplied as calibration standards; those are custom-blended by the batch to within 1% of the target. AFAIK, collodion just isn’t that critical.