Depression without mania is sometimes referred to as unipolar because the mood remains at one emotional state or "pole".Bereavement is not an exclusion criterion in DSM-5, and it is up to the clinician to distinguish between normal reactions to a loss and MDD. Excluded are a range of related diagnoses, including dysthymia, which involves a chronic but milder mood disturbance; recurrent brief depression, consisting of briefer depressive episodes; minor depressive disorder, whereby only some symptoms of major depression are present; and adjustment disorder with depressed mood, which denotes low mood resulting from a psychological response to an identifiable event or stressor. Subtypes
The DSM-5 recognizes six further subtypes of MDD, called specifiers, in addition to noting the length, severity and presence of psychotic features:

"Melancholic depression" is characterized by a loss of pleasure in most or all activities, a failure of reactivity to pleasurable stimuli, a quality of depressed mood more pronounced than that of grief or loss, a worsening of symptoms in the morning hours, early-morning waking, psychomotor retardation, excessive weight loss (not to be confused with anorexia nervosa), or excessive guilt. "Atypical depression" is characterized by mood reactivity (paradoxical anhedonia) and positivity, significant weight gain or increased appetite (comfort eating), excessive sleep or sleepiness (hypersomnia), a sensation of heaviness in limbs known as leaden paralysis, and significant long-term social impairment as a consequence of hypersensitivity to perceived interpersonal rejection. "Catatonic depression" is a rare and severe form of major depression involving disturbances of motor behavior and other symptoms.
For example, it reduces nitric acid to nitrogen monoxide and chlorine to chloride:

6 FeSO4 + 3 H2SO4 + 2 HNO3 → 3 Fe2(SO4)3 + 4 H2O + 2 NO
6 FeSO4 + 3 Cl2 → 2 Fe2(SO4)3 + 2 FeCl3Its mild reducing power is of value in organic synthesis. It is used as the iron catalyst component of Fentons reagent. Ferrous sulfate can be detected by the cerimetric method, which is the official method of the Indian Pharmacopoeia. This method includes the use of ferroin solution showing a red to light green colour change during titration. See also
Iron(III) sulfate (ferric sulfate), the other common simple sulfate of iron. Copper(II) sulfate
Ammonium iron(II) sulfate, also known as Mohrs salt, the common double salt of ammonium sulfate with iron(II) sulfate. Chalcanthum
Ephraim Seehl known as an early manufacturer of Iron(II) sulfate, which he called green vitriol. References
External links

"Ferrous sulfate". Drug Information Portal. U.S. National Library of Medicine.