Lactose aqueous soln.

[Bill]

Hi Group,

Anyone have any experience putting lactose into aqueous solns? I'd
like to have it as concentrated as possible to start; literature cites
0.216 g/mL in H2O but I get nothing near that, even with heat and 100
mM NH4OAc buffer (not a true buffer, no acetic acid present, NH4OAc is
more of a pH modifier than true buffer). Solutions are slightly to
very turbid. I haven't found pKa of lactose, but that may help!

I've also noticed that once you freeze the solns, lactose drops out
lick a rock once frozen, which is OK and prefered and desired, but I
want to get lactose completely solvated first before the flash freeze
crash. Are very concentrated lactose solns. turbid or clear?

Thanks in advance for any tips, tricks or suggestions!

Regards to all in the group,

WB

[d***@gmail.com]

Anyone have any experience putting lactose into aqueous solns?  I'd
like to have it as concentrated as possible to start; literature cites
0.216 g/mL in H2O but I get nothing near that,

No experience with lactose, but many carbohydrates take a long time to
dissolve at high concentrations, as in days or weeks. Compare the time
it takes to dissolve 40% sucrose compared to 10%, for example. As more
and more water is tied up in hydrogen bonds to the sugar, the mobility
of the remaining water is greatly reduced. This also shows up as
increased viscosity.

Consider that the final product may be too syrupy to measure
conveniently. What happens at 0.1 g/mL?

DB

[d***@gmail.com]

Post by d***@gmail.com
Consider that the final product may be too syrupy to measure
conveniently. What happens at 0.1 g/mL?

Also, lose the AmAc. It's competing for water, too.

DB

[s***@msn.com]

Post by d***@gmail.com

Post by d***@gmail.com
Consider that the final product may be too syrupy to measure
conveniently. What happens at 0.1 g/mL?

Also, lose the AmAc. It's competing for water, too.
DB

Excellent sir... thank you! Am I spinning my wheels with the pH/pKa
trying to get it in? Again, many thanks!

WB

[d***@gmail.com]

Excellent sir... thank you!  Am I spinning my wheels with the pH/pKa
trying to get it in?  

Probably. There should be no noticeable pH reaction, and if there is,
it may be distorted by the great reduction in water activity.

DB

[The Mad Alchemist]

Post by d***@gmail.com

Anyone have any experience putting lactose into aqueous solns?  I'd
like to have it as concentrated as possible to start; literature cites
0.216 g/mL in H2O but I get nothing near that,

No experience with lactose, but many carbohydrates take a long time to
dissolve at high concentrations, as in days or weeks.

Lactose is quite slow to dissolve and to crystallize- an organic
course I once supervised had a lab where the lactose was extracted
from skim milk powder, and it took a week (or at least several days)
to crystallize from a supersaturated solution.

[Marvin]

Post by The Mad Alchemist

Post by d***@gmail.com

Post by Bill
Anyone have any experience putting lactose into aqueous solns? I'd
like to have it as concentrated as possible to start; literature cites
0.216 g/mL in H2O but I get nothing near that,

No experience with lactose, but many carbohydrates take a long time to
dissolve at high concentrations, as in days or weeks.

Lactose is quite slow to dissolve and to crystallize- an organic
course I once supervised had a lab where the lactose was extracted
from skim milk powder, and it took a week (or at least several days)
to crystallize from a supersaturated solution.

I remember a prof telling my class, ca. 1948, that sugar
chemists had beards that served to store seed crystals, so
they got crystals from solution faster. Not likely, but a
nice legend. An alternate version had the seed crystals in
the laboratory's dust. Either one suggests that cleanliness
in the lab isn't always a good thing.

[spm_sux]

Post by Marvin

Post by The Mad Alchemist

Post by d***@gmail.com

Anyone have any experience putting lactose into aqueous solns?  I'd
like to have it as concentrated as possible to start; literature cites
0.216 g/mL in H2O but I get nothing near that,

No experience with lactose, but many carbohydrates take a long time to
dissolve at high concentrations, as in days or weeks.

Lactose is quite slow to dissolve and to crystallize- an organic
course I once supervised had a lab where the lactose was extracted
from skim milk powder, and it took a week (or at least several days)
to crystallize from a supersaturated solution.

I remember a prof telling my class, ca. 1948, that sugar
chemists had beards that served to store seed crystals, so
they got crystals from solution faster.  Not likely, but a
nice legend.  An alternate version had the seed crystals in
the laboratory's dust. Either one suggests that cleanliness
in the lab isn't always a good thing.

That's a good story! I think sugar chemists have beards from waiting
for their carbs to go into solution! Thanks to all who replied.