Found in the Regulations for the Army of the Confederate States, Article XII, Regiments, #68 we find:
"The commander of a regiment will appoint the adjutant from the subalterns of the regiment."
Further under the table of Pay and Allowances for the Army, First Lts received $90 per month, 2nd Lts, $80. then, Adjutant in addition to pay of Lieutenant, $10 per month.
An example of the background of the Adjutant of the 43rd Tennessee Infantry, CSA is that of Summerfield Key:
Key, Summerfield Armitage, Adjutant, born October 14, 1834 in Monroe Co., Tenn., graduated from Hiwasee College then entered upon the study of law, transferred from Co. A, 19th Regt. Tenn. Vols. November 15,1861, promoted from Pvt. to Adjutant December 14, 1861, post-war, original member of Lookout Volunteer Fire Deptartment [Lookouts], two years served as member of the Tennessee General Assembly, Chancellor the the Third chancery division of Tennessee, member N. B. Forrest UCV Camp #3 of Chattanooga, died June 14, 1891, brother David McKendree Key, regimental Lt. Col.
His file shows that he received the pay of $100 per month and all his CSR cards, including his Vicksburg parole papers, carry his rank as that of Adjutant.
I have been unable to locate the actual duties of an Adjutant, but perhaps the book described below, may be of interest.
Civil War Books
"In many respects the best regimental history for a Civil War unit; ... "Written from the adjutant's viewpoint,this full history of a year's duty ...
www.wardhousebooks.com/NewHampshire.html - 22k - Cached - Similar pages
NewHampshire.htmlHISTORY OF THE SIXTEENTH REGIMENT NEW HAMPSHIRE VOLUNTEERS.
By Luther Townsend. Washington D.C.,1897.
575 Pages, Illustrated. $49.00
"Written from the adjutant's viewpoint,this full history of a year's duty
in Louisiana also contains over twoscore sketches and drawings." CWB