ACETATES AND THEIR MANUFACTURE. 295 



chrome red. Upon the cloth-fibre (especially wool) chrome yel- 

 low and chrome orange are produced by means of sugar of lead, 

 especially with the brown variety ; the latter product being also 

 very suitable for the production of the so-called chrome green, 

 which is obtained by the joint precipitation of chrome yellow and 

 Berlin blue. 



Xeutral lead acetate gives crystallizable double salts with 

 potassium acetate and sodium acetate as well as with lead nitrate, 

 lead chloride, lead bromide, etc. 



Basic lead acetates. Several of these compounds are known. 

 Those with 2 and 3 equivalents of plumbic oxide to 1 equivalent 

 of acetic acid are soluble in water, show a strong alkaline reac- 

 tion, and with carbonic acid the solutions yield at once and in 

 every degree of concentration abundant precipitates of white lead 

 (basic carbonate of lead), while, when the operation is at a suita- 

 ble moment interrupted, neutral salt remains in solution. In this 

 manner white lead is manufactured according to the so-called 

 French method (of Thenard and Hoard) at Clichy and other 

 places in France as well as in different German factories. If, 

 however, the introduction of carbonic acid be continued until no 

 more precipitate is formed, a part of the lead of the neutral salt 

 is also precipitated as carbonate, which, however, is neutral, and 

 an acid solution remains behind. 



The soluble salt known as lead-vinegar or extract of lead is pre- 

 pared by digesting 2 parts of sugar of lead dissolved in 5 of 

 water with 1 of finely powdered litharge. The proportional 

 quantities of sugar of lead, litharge, and water prescribed by the 

 Pharmacopoeias of the different countries vary very much, and, 

 consequently, also, the compositions and specific gravities (from 

 1.20 to 1.36) of the solutions of lead prepared in accordance witli 

 them. The litharge dissolves very readily in the sugar of lead 

 solution, in fact with greater ease than in acetic acid, and espe- 

 cially with greater rapidity if the sugar of lead solution be heated 

 in a silver dish to the boiling point and the litharge gradually 

 introduced. For the manufacture on a large scale, the sugar of 

 lead solution and the litharge may be brought into a barrel revolv- 

 ing around its axis. If the operation is to be conducted at the 

 ordinary temperature, the barrel must be closed to prevent the 



