On food and cooking the science and lore of the kitchen ( PDFDrive ) 1477

The same principal is put to use tospeed
cookinginthepressurecooker.Thisappliance
reduces cooking times by trapping the steam
that escapes from boiling water, thereby
increasing the pressure on the liquid, and so
raising its boiling point — and maximum
temperature — to about 250ºF/120ºC. This is
theequivalentofboilingwaterinanopenpan
atthebottomofapit19,000feet/5,800meters
belowsealevel.
Thepressurecookerwasinventedbythe
FrenchphysicianDenisPapininthe17th
century.
The Boiling Point Is Increased by Dissolved
SugarandSaltWhensalt,sugar,oranyother
water-soluble substance is added to pure
water, the boiling point of the resulting
solutionbecomeshigherthantheboilingpoint
of water, and the freezing point lower than
water’sfreezingpoint.Botheffectsaredueto
the fact that the water molecules are diluted


by the dissolved particles, which interfere
withthewatermoleculesastheychangephase
from liquid to gas or liquid to solid. In the
caseoftheboilingpoint,thesolutioncontains
sugar molecules or salt ions that also absorb
heatenergy,butcannotthemselvesturnintoa
gas.Soatwater’snormalboilingpoint,there
is a smaller proportion of molecules with

enough energy to escape from the liquid and
form a bubble of vapor, and the cook has to
add more energy than usual in order to get
those bubbles to form. The boiling point and
freezing point rise and fall predictably as the
concentration of dissolved sugar or salt
increases,afactthatishandyformakingboth
sugarcandiesandicecreams.
It’struethataddingsalttowaterraisesits
boilingpoint,andsospeedscooking.
However,ittakesoneounceofsaltinaquart
ofwater—aroundthesalinityoftheocean—
toraisetheboilingpointanegligible1ºF.A
Denveritewhowantedtoboilwateratthe