Lead sulfide (also spelled sulphide) is an inorganic compound

Inorganic compound

Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with the formula

Chemical formula

A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 Pb

Lead

Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

. It finds limited use in electronic devices. PbS, also known as galena

Galena

Galena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...

, is the principal ore and most important compound of lead.
Addition of hydrogen sulfide or sulfide salts to a solution of lead ions gives a poorly soluble black product consisting of PbS:

Pb²⁺ + H₂S → PbS + 2 H⁺

The equilibrium constant for this reaction is 3 M.
This reaction, which entails a dramatic color change from colourless or white to black, was once used in qualitative inorganic analysis

Qualitative inorganic analysis

Classical qualitative inorganic analysis is a method of analytical chemistry which seeks to find elemental composition of inorganic compounds. It is mainly focused on detecting ions in an aqueous solution, so that materials in other forms may need to be brought into this state before using standard...

.