434 On the late Lunar Occult at ion of Jupiter. 



two bodies were coml)ined, I transformed them into sulphuric 

 and chromic acids by means of nitrate of potash, and I deduteci 

 the (|uantity of sulphur from that of the sulphate of harytes, ob- 

 tained by precipitating the solution of the residue of that cal- 

 cination by the nitrate acid of barytes. 



According to the mean result of the two experiments, I con- 

 cluded that the sulphuret of chrome, which I had prepared, was 

 formed as follows : 



Chrome 1 00-00 



Sulphur 10-54 



These experiments led me to a more prompt and oeconomical' 

 method of preparing oxide of chrome of a beautiful green co- 

 lour, and which may always be oljtained of the same degree of 

 intensity. 



This method consists in calcining to redness^ in a hard 

 earthen crucible, a mixture of the chromate of potash and sul- 

 phur, in equal parts, and steeping in water the greenish mass 

 which remains, in order to dissolve the sulphate and the sulphuret 

 of potash which are formed by that operation. The oxide of 

 chrome is precipitated, and may be obtained pure after several 

 washings. 



It is not necessary to have the chromate of potash crystallised, 

 in order to extract from it bv this process the oxide of chrome. 

 I have also obtained a beautiful colour by calcining with the sul- 

 phur the produce of the evaporation of a solution of chromate 

 of iron treated with nitre, which I had previously saturated by 

 dilute sulphuric acid, in order to precipitate the alumineand silex 

 which very often accompany that mineral. 



LXX. On the late Lunar Occultaiion oj Jupiter ; with Remarks 

 on the late Solar Eclipse. By Mr. George Innes, Aberdeen. 



To Mr. Tilloch, 



Sir, — J- HAVE just seen the last Number of your valuable Ma- 

 gazine ; and, finding no account of any observation being made of 

 the late occultation of Jupiter by the Moon, I send you the ele- 

 ments for calculation, and likewise the result of a calculation of 

 the time of last external contact for Aberdeen. 



The elements from the lunar tables of M. Burckhardt, and 

 the tables of the Sun and Jupiter in Professor Vince's 3d vol. of 

 Astronomy, are as follows : 



Apparent 



