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A diamond knife uses a sharpened diamond edge to cut ultrathin sections in ultramicrotomy. The edge's geometry and condition affect the force applied to the specimen and the resulting section. JEOL describes its use for hard inorganic materials and for obtaining uniform sections from resin specimens.^[ref]

The knife wedge angle is the angle between the blade faces. It differs from the knife clearance angle, which concerns how the blade is oriented relative to the freshly cut surface. Manufacturer descriptions include $35^{\circ }$ and $45^{\circ }$ knife families, with the lower-angle design promoted for reduced section compression and a higher-angle design discussed for hard materials.^[ref]

For an original ideal symmetric wedge of included angle $\beta$, the blade width a distance $h$ behind the apex isAt $h=1\mu \mathrm{m}$, this gives $w\simeq 0.631\mu \mathrm{m}$ for $\beta =35^{\circ }$ and $w\simeq 0.828\mu \mathrm{m}$ for $\beta =45^{\circ }$. The wider ideal wedge has about 31% more material behind the edge at that distance. This illustrates a geometry tradeoff; it does not predict a 31% difference in cutting force or assert the exact profile of a commercial knife.

A useful materials experiment compares otherwise matched cuts while recording knife orientation, feed and specimen condition, then measures section dimensions and surface defects. A cut stripe that repeats at the same lateral position suggests an edge-related artifact worth checking. Diamond hardness alone does not guarantee an undamaged edge or an undistorted section.

Guaiacum resin is a resin obtained from Guaiacum wood. It is a complex plant product whose solubility and oxidation behavior have been used in historical chemical tests.

Jalap is a medicinal material derived from the storage root of a climbing plant. The source tissue and its extracted resin are distinct preparations.

Mistura Guaiaci is a guaiacum-resin mixture. The dispersed resin and aqueous vehicle have different physical properties.^[ref]

Mistura Scammonii is a scammony-containing mixture. A mixed liquid preparation differs from the isolated resin fraction.^[ref]

Myrrh is an aromatic gum-resin obtained from Commiphora plants. Its water-binding gum, resin and volatile constituents contribute different physical properties.

The seven named mixtures of the 1864 British Pharmacopoeia are Mistura Ammoniaci, Mistura Amygdalae, Mistura Creasoti, Mistura Cretae, Mistura Ferri Composita, Mistura Guaiaci and Mistura Scammonii. Their compositions are as follows; avoirdupois ounces are used for solids and fluid ounces for liquids.

The category is an official preparation name, not every possible bedside combination of medicines. Camphor water and acacia mucilage are not additional entries under Mistura: the 1864 names are Aqua Camphorae and Mucilago Acaciae. ^[ref]

A colloidal grain in a liquid is large enough to see with a microscope, yet small enough for thermal motion to compete with its tendency to settle. In the Perrin sedimentation experiment, the equilibrium number density falls with height: a visible miniature atmosphere. Counting grains at different heights measures an energy scale; tracking their Brownian motion measures a transport rate. Connecting both to the same Avogadro constant makes the experiment a quantitative test of kinetic theory. The Wiener measure describes an idealized path law; these measurements instead test a physical model and its material parameters.

Jean Baptiste Perrin's 1909 memoir traces his sedimentation experiments to May 1908. It reports relative counts $100$, $47$, $22.6$, $12$ at heights $5$, $35$, $65$, $95\mu \mathrm{m}$, and compares radius estimates from Stokes settling velocity, counted grain mass, and rows of touching grains.^[ref]

The 1926 lecture describes resin precipitated from alcohol into water, washed and fractionated by centrifugation to obtain nearly monodisperse gamboge or mastic grains. Diameter and density were measured separately. A sealed slide-and-cover-glass chamber prevented evaporation; a vertical microscope resolved roughly $2\mu \mathrm{m}$ layers through a roughly $0.1\mathrm{mm}$ depth. Refocusing and photographing compared layer populations after equilibrium; changing temperature reversibly changed the distribution.^[ref]

In Les Atomes (1913), Jean Baptiste Perrin restricts the eyepiece view to fewer than five or six grains and alternates observations between heights. Focus displacement requires a refractive index correction to recover actual layer separation. Horizontal positions were marked with a camera lucida, usually every $30\mathrm{s}$, and distances calibrated with a micrometer; the polygon joins sampled positions rather than recording the intervening trajectory.^[ref][ref]

A resin is a broad material category covering many natural or synthetic organic substances used as solid or hardenable binding materials. Some are mixtures of small molecules; others contain polymers or reactive precursors.

The term alone therefore gives neither a unique formula nor a complete curing mechanism. Whether a resin hardens by solvent loss, cooling, or formation of new chemical crosslinks must be specified for the particular material.

Scammony resin is a resinous preparation obtained from scammony material. The isolated resin fraction differs from the crude plant product.