Manual of basic techniques for a health laboratory - libdoc.who.int

246 Manual of basic techniques for a health laboratoryFig. 7.25 Triple phosphate crystalsa: Rectangular-shaped crystals; b: fernleaf-shaped crystals.Fig. 7.26 Urate crystalsa: Cactus-shaped crystals; b: needleshapedcrystals.Fig. 7.27 Calcium phosphatecrystalsFig. 7.28 Calcium carbonate crystalsUrates (alkaline urine) (Fig. 7.26)Size: about 20mm.Shape: like a cactus (a) or a bundle of needles (b).Colour: yellow, shiny.Urates are often found together with phosphates.Calcium phosphate (neutral or alkaline urine) (Fig. 7.27)Size: 30–40mm.Shape: like a star.Colour: colourless.Calcium carbonate (neutral or alkaline urine) (Fig. 7.28)Size: very small.Shape: similar to millet or corn grains, grouped in pairs.Colour: colourless.If acetic acid, 10% solution (reagent no. 2) is added, the crystals dissolve, giving offbubbles of gas.Calcium sulfate (acid urine) (Fig. 7.29)Size: 50–100mm.Shape: long prisms or flat blades, separate or in bundles.Calcium sulfate crystals can be distinguished from calcium phosphate crystals bymeasuring the pH of the urine.Amorphous debrisAmorphous phosphates (alkaline urine) (Fig. 7.30)Amorphous phosphates appear as small, whitish granules, often scattered.