=Neutral Lead Chromate=, PbCrO₄, is formed as a very heavy precipitate of a fine deep yellow colour when a solution of potassium chromate or bichromate is added to a solution of a lead salt in water. When exactly equivalent quantities of potassium chromate and lead solution are used, and the strength of the solutions is the same, the product has the same shade each time the operation is performed. It is not immaterial whether the one or the other salt is in excess, or whether strong or weak solutions are used; all these conditions modify the shade of the chrome yellow produced. Many colour makers are apparently of the opinion that some particular skill of the workman is necessary to produce chrome yellow of a particular shade. This is, however, not the case; manufacturers who know the simple conditions which are important in making chrome yellows may produce any desired shade without difficulty. Neutral lead chromate readily parts with half the chromic acid it contains. When treated with alkalis, such as lime or caustic soda, or even when digested with finely ground litharge, the neutral salt gives up half of its chromic acid, and is converted into the basic chromate or chrome red, Pb₂CrO₅. Basic lead chromate has, as the name chrome red indicates, a fine red colour. If the quantity of lime or caustic soda used is sufficient to decompose only a portion of the neutral lead chromate, a mixture of the yellow neutral and the red basic chromate is formed, the shade of which will incline to yellow or red according as it contains a preponderance of one or the other compound. The pigment known as orange chrome is a mixture of approximately equal parts of the neutral and basic lead chromates. In order to brighten the deep yellow shade which distinguishes neutral lead chromate, it is either mixed with a white pigment, or a white substance (lead sulphate) is precipitated from the solution simultaneously with the lead chromate. In this manner all the imaginable pale yellow shades, lemon yellow, sulphur yellow, etc., can be obtained.