Chemical Science, 161 



The effect is greater the higher the temperature is raised, and 

 the more rapidly it is done ; and M. Bellani attributes it to the 

 slower contraction of the glass, after having been expanded by 

 heat, as compared with that of the mercury. He refers to it as 

 an unavoidable source of error in all delicate thermometrical 

 operations, as in the barometrical thermometer, &c. 



13. Blue Iris Test Colour. — Professor Ormstead of North 

 Carolina University, recommends the tincture of the petals of 

 the garden iris, or blue lily, as superior to every other test 

 liquor known. It is reddened as litmus is, by blowing through 

 it, or by a stream of carbonic acid gas. It is more convenient 

 than violets, from the abundance of colouring matter contained 

 in the petals ; and it is said to be superior to red cabbage tinc- 

 ture, as well for its permanency as its delicacy. Of the former 

 cause of superiority there may be doubts. This application of 

 the petals of the blue iris has long been known to us ; by rub- 

 bing them upon paper, we form a very convenient test either 

 for acids or alkalies. 



14. Succinic Acid in Turpentine — MM. Lecanu and Serbat 

 have ascertained with certainty the presence of succinic acid in 

 turpentine. It rises when the oil is distilled, towards the end 

 of the operation, and has all the properties of true succinic 

 acid. They have pointed out also, that the presence of acetic 

 acid takes from succinic acid the power of forming precipitates, 

 with preparations of iron, copper, lead, or barytes. Neither 

 will a mixture of acetate and succinate of potash precipitate 

 these substances ; on the contrary, the succinates, when pro- 

 duced, are soluble without difficulty, in a sufficient quantity of 

 acetate of potash. — Annales de Chim. xxi. 328. 



1.5. Cinnabar. — M. KirchofF prepares cinnabar in the follow- 

 ing manner. Triturate in a porcelain cup with a glass pestle 

 300 parts of mercury with 68 of sulphur moistened with some 

 drops of a solution of potash till a black proto-sulphuret is 

 formed, and then add 160 parts of potash, dissolved in an 

 equal quantity of water. Heat the vessel containing the mix- 

 ture over the flame of a candle or lamp, continuing the tritu- 

 ration without intermission. Add pure water from time to time 

 as the liquid evaporates, that the substance may be constantly 

 covered an inch deep. After two hours continued trituration, 



