defined by the sum of the number of protons and neutrons
in its nucleus. Elements have more than one isotope with
varying numbers of neutrons. For example, there are two
common isotopes of carbon, 12C and 13C which have 6
and 7 neutrons respectively. The abundances of different
isotopes of elements vary in nature depending on the source
of materials. For relative abundances of isotopes in nature
see reference on Isotopic Composition of the Elements.
Atomic weight values represent weighted average of
the masses of all naturally occurring isotopes of an
element. The values shown here are based on the IUPAC
Commission determinations (Pure Appl. Chem. 73:667-
83, 2001). The elements marked with an asterisk have
no stable nuclides. For these elements, the weight value
shown represents the mass number of the longest-lived
The distribution of electrons according to the energy
sublevels (subshells) in uncharged atoms. The noble gas
shown in square brackets (e.g. [He]), marks that all the
subshells associated with that element are fully occupied
PERIODIC TABLE OF THE ELEMENTS
Urine composition is affected mainly by three factors:
2. State of metabolic processes
3. Ability of the kidney to selectively handle the material
Physiochemical Characteristics of Urine
Osmolality 38–1400 mOsm/kg water
Inorganic Constituents per 24 Hours
Chlorides 6 (4–10) g on usual diet
Phosphate 0.8–1.3 g on usual diet
Organic Constituents per 24 Hours
Creatine, in children 10–50 mg (excreted in urine
in adults in hepatic or muscle
Glucose (fasting range) 2–20 mg%
Amylase (diastase) 40–260 units/hour.
Leukocytes Up to 5 million/hour
Epithelial cells Up to 2.5 lakh/hour
The urine sample should be collected in a clean, dry
container and should be examined fresh. For cultures,
sterile containers should be used. With time, RBC, and
leucocytes tend to be destroyed due to hypotonicity of
the urine. Casts too tend to get decomposed. Bacterial
contamination of stale urine is frequent and causes
alkalinization of the urine due to conversion of urea to
ammonia and loss of glucose. This rise in pH accelerates
loss of leucocytes and epithelial cells. For ordinary
qualitative, tests a random sample is enough. For diabetes
mellitus, a 2-hour postprandial sample is desirable; for
nephritis, a morning specimen is best as it has higher
specific gravity and lower pH desirable for preservation of
Repeated samples are necessary sometimes, as for
Whenever needed, a 24-hour urine should be collected
in a large container. Have patient void and discard urine
at any particular time, save all urine for the next 24 hours,
and then void at the same hour to finish the collection.
if not, then it should be refrigerated. As far as possible,
the need for preservation should not arise. However, the
following preservatives can be used:
1. Toluol Best for preservation of chemical constituents. Add 2 mL toluol/100 mL urine.
2. Thymol A small floating lump of thymol can
preserve the urine for several days in a
bottle. Thymol may, however, cause a
false-positive reaction for protein.
3. Formalin 1 drop/30 mL urine. Is good for preserving
formed elements. It can precipitate
proteins and can reduce Benedict’s
4. Boric acid 0.3 g/120 mL of urine. However, yeasts
can still grow and uric acid crystals get
Normal urine is clear and pale yellow (straw) in color.
1. Colorless: Dilution; diabetes mellitus/insipidus,
nervousness, diuretic or alcohol intake.
2. Milky: Purulent genitourinary tract disease; chyluria.
3. Orange: Urobilinogenuria, fever, excessive sweating,
4. Red: Beetroot ingestion, hematuria, hemoglobinuria,
phenolphthalein, pyridinium sulfo♥nate.
5. Greenish: Jaundice, phenol poisoning.
6. Dirty blue or green: Putrefying urine, in typhus or
7. Dark brown, brown red, or yellow: Very concentrated
urine, acute febrile diseases, bilirubinuria.
8. Brown-yellow or brown red (if acidic) or bright red (if
alkaline): Due to rhubarb, cascara, aloes.
9. Brown, brown black or black: Hemorrhage in urinary
tract if urine is acidic (Acid-hematin); hemoglobinuria;
porphyria, methemoglobinuria; myoglobinuria,
melanin, phenol poisoning, homogentisic acid (alkaptonuria). In porphyria, urine turns dark brown on
exposure to sunlight or boiling.
¾ Normally, urine darkens on standing. This occurs
because of oxidation of urobilinogen to urobilin.
Decomposition of urine commences in half an hour.
¾ Some foods cause change in urine color
• Rhubarb changes color of urine to brown.
¾ Many drugs are also responsible for urinary color change
• Cascara and senna laxatives in acidic urine will turn
the urine reddish-brown, in alkaline urine they will
• Phenazopyridine (pyridium), amido pyrine turn
• Pyridium, ethoxazene turn urine to orange/orange red
• Orange to purple red may occur due to chlorzoxazone
• Salicylazosulfapyridine, anisindone, or phenindione
turn urine color to orange-yellow in alkaline urine
• Sulfonamides and nitrofurantoins produce rustyellow to brownish color
• Dilantin (diphenylhydantoin) dioctyl calcium
sulfosuccinate, phenolphthalein and phenothiazine
turn urine color to pink to red or red-brown
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