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Hazard pictograms, apparatus notation and the marks on reagent bottles.
GHS hazard pictograms are the best-standardised set here: nine pictograms, defined internationally, each with a published hazard class behind it. They are worth learning precisely because they are consistent across countries in a way most symbol systems are not.
These records say so themselves — the setting appears in the symbol's own reviewed description or in one of its documented meanings.
A form resembling a crossed or looped stroke, denoting ammonium chloride.
Its a documented meaning places it there: “…sal ammoniac, ammonium chloride, a salt valued in the laboratory because it sublimes readily and could be used…”
A sign for a water bath, giving gentle and controlled heat.
Its a documented meaning places it there: “Survives unchanged in modern cooking and laboratory practice, where the same principle gives controlled heat…”
A looped form resembling a script V or a hooked stroke, denoting sulphate salts.
Its a documented meaning places it there: “…modern esoteric writing far exceeds its role in laboratory practice”
These carry an editorial context assigned during review that places them here.
Showing the 48 most firmly placed of 269. Browse by domain to see every symbol in the catalogue.
A capital K with a lowercase a subscript.
An italic capital S, the integral of the Lagrangian over time.
A Greek gamma, correcting concentration to effective concentration.
An italic capital Y, the reciprocal of impedance.
A capital F marking points on every face.
A fixed frame for the body.
A Greek omega, radians per second rather than cycles per second.
A capital L, rotational momentum about an axis.
A plain lowercase a, removing one quantum.
A Greek alpha or beta — a small curved letter — before a sugar's name.
An overbar marking a particle's antimatter counterpart.
Standard outlines for flasks, condensers and joints.
The letters aq in brackets after a formula.
Coordinate ranges bounding the smallest unique part.
A name and a date after a species.
A capital N with subscript A, the number of entities in a mole.
A dashed line marking a glide along an axis.
A unit of area for nuclear reaction probability.
An italic capital B, one third per quark.
A straight-sided cylinder with a pouring lip.
A circle inside a hexagon, standing for delocalised electrons.
A hexagon with an inscribed circle, representing delocalised aromatic bonding.
A trefoil of overlapping circles, designed to be instantly recognisable as a warning for biological hazards.
A number from one to four rating containment.
A capital I marking a lattice point at the cell centre.
A Greek mu with a capital B subscript, the electron's magnetic unit.
An italic a with a nought subscript, the atomic length scale.
A wider tube for heating larger quantities.
An italic k, often subscripted B, relating temperature to energy.
Angle brackets and a bar denoting quantum states.
Four figures used for hexagonal crystals.
A theta with a B subscript, the angle of complete polarisation.
A Greek mu with a raised numeral, before a ligand's name.
A flat perforated plate above a stem.
A vertical barrel on a base with a gas inlet.
A long graduated tube with a tap at its foot.
Digits in three hyphen-separated groups, the last a single check digit.
A formula written above a reaction arrow, naming a catalyst.
A single upright stroke, marking a phase boundary.
A capital C, swapping every particle for its antiparticle.
A Greek mu, the energy cost of adding one more particle.
A capital gamma with one raised and two lowered indices.
Letters p and q naming the two arms.
Numbers locating a band on an arm.
A del with bracketed position.
An inv with bracketed breakpoints.
A t with bracketed chromosomes and breakpoints.
Plane indices naming a preferred break.
If you can describe what you saw as well as where, say both: “winged skull on a gravestone” narrows a list of 272 to a handful.