Chemical Science. 347 



number of degrees against that temperature on the ther mometer, 

 as obtained in an atmosphere saturated with water, and the result 

 expresses the ratio of the water in that atmosphere to a saturated 

 atmosphere considered as unity. 



This is a curious application of the heat occasioned by the union 

 of water and sulphuric or other acids ; but of course has no pre- 

 tensions to the accuracy of that philosophical instrument Daniell's 

 Hygrometer, nor has any other instrument with which we are 

 acquainted. — Bib. Univ. April 1825. 



18. Ejoposure of Iron to Air in high Regions. — In one of the ex- 

 cursions made by M. Zumstein and others to the summit of Monte 

 Rosa, an iron cross was fixed upon it and left there. This was in 

 August 1820. M. Zumstein again ascended the mountain in 

 August 1821, and after great risks reached the summit and the cross . 

 The latter was found not at all rusted, but had taken the colour 

 of bronze. The barometer was at 16 inches 4.2 lines. The tem- 

 perature of the air was — 0.5 R (21°F.), and by calculation the 

 height was obtained as 14,086 feet. Water boiled at 68.38° R. 

 (185.°8 F.]-'Bib. Univ. xxviii. 65. 



19. Applications of Chromate of Lead in the Arts. — In a paper 

 published in the Annals of Philosophy., N.S. ix. 303, Mr. Badams 

 describes the results of certain experiments on the composition of 

 the scarlet or sub-chromate of lead, and the yellow chromate, 

 and highly recommends the use of the former, as a colour either 

 in painting, or calico-printing. 



He prepares the red chromate by boiling the yellow chromate 

 with potash, a process devised by Grouvelle. Upon digesting 

 100 grains of this scarlet chromate in diluted acetic acid for 

 half an hour, and constantly stirring, the substance became of 

 a pure yellow colour, and was found when washed to weigh only 

 60 grains, acetate of lead remaining in solution. On the con- 

 trary, grinding 60 grains of yellow chromate with 40 grains of 

 oxide of lead with the addition of small quantities of hot water 

 from time to time, the red sub-chromate was again produced. 

 After some further experiments, Mr. Badams gives the compo- 

 sition of the yellow chromate Red chromate. 

 Chromic acid 1 atom 19.02 - - 1 atom 19.02 



Oxide of lead 1 40.98 - - 2 atoms 81.96 



Having made many experiments upon the properties of the 

 scarlet chromate as a fast colour in calico-printing, and a durable 

 pigment for artists in oil and water, he states that with respect 

 to the first object, the practice of the calico-printer in making the 

 yellow chromate fast, will teach him how to apply the red chro- 

 mate ; the colour being given to him by nitrate of lead and an al- 

 kaline solution of chromate of potash. He may accumulate be- 



